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Full text of "Formaldehyde and Other Aldehydes"

Formaldehyde 

and Other Aldehydes 

Committee on Aldehydes 

Board on Toxicology and Environmental Health Hazards 

Assembly of Life Sciences 

National Research Council 



NATIONAL ACADEMY PRESS 
Washington, DC 1981 



FY 



NOTICE: The project that is the subject of this report was approved 
by the Governing Board of the National Research Council, whose members 
are drawn from the councils of the National Academy of Sciences, the 
National Academy of Engineering, and the Institute of Medicine. The 
members of the Committee responsible for the report were chosen for 
their special competences and with regard for appropriate balance . 

This report has been reviewed by a group other than the authors 
according to procedures approved by a Report Review Committee 
consisting of members of the National Academy of Sciences, the 
National Academy of Engineering, and the Institute of Medicine. 

The National Research Council was established by the National 
Academy of Sciences in 1916 to associate the broad community of 
science and technology with the Academy's purposes of furthering 
knowledge and of advising the federal government. The Council 
operates in accordance with general policies determined by the Academy 
under the authority of its congressional charter of 1863, which 
establishes the Academy as a private, nonprofit, self-governing 
membership corporation. The Council has become the principal 
operating agency of both the National Academy of Sciences and the 
National Academy of Engineering in the conduct of their services to 
the government, the public, and the scientific and engineering 
communities. It is administered jointly by both Academies and the 
Institute of Medicine. The National Academy of Engineering and the 
Institute of Medicine were established in 1964 and 1970, respectively, 
under the charter of the National Academy of Sciences. 

The work on which this publication is based was performed pursuant 
to Contract 68-01-4655 with the Office of Research and Development of 
the Environmental Protection Agency (Dr. Alan P. Carlin, Project 
Officer) . 

Library of Congress Catalog Card Number 81-81738 
International Standard Book Number 0-309-03146-X 

Available from: 

NATIONAL ACADEMY PRESS 

2101 Constitution Ave., N.W. 

Washington, D.C. 20418 

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^ 

* Printed in the United States of America 

V 



COMMITTEE ON ALDEHYDES 

JACK G. CALVERT, Ohio State University, Columbus, Ohio, Chairman 
LYLE F. ALBRIGHT, Purdue University, West Lafayette, Indiana 
EILEEN BRENNAN, Cook College, New Brunswick, New Jersey 

STUART M. BROOKS, University of Cincinnati School of Medicine, 
Cincinnati, Ohio 

CRAIG D. HOLLOWELL, University of California, Berkeley, California 
DAVID H. W. LIU,* Woodward-Clyde Consultants, San Francisco, California 

CHARLES F. REINHARDT, Haskell Laboratory, E. I. du Pont de Nemours & 
Company, Wilmington, Delaware 

JAMES A. FRAZIER, National Research Council, Washington, D.C., Staff 
Officer 

NORMAN GROSSBLATT, National Research Council, Washington, D.C., Editor 

LESLYE B. GIESE, National Research Council, Washington, D.C., Research 
Assistant 

JEAN E. PERRIN, National Research Council, Washington, D.C., Secretary 



*Early in the preparation of this report, Dr. Liu was with SRI 
International, Menlo Park, California. 



111 



BOARD ON TOXICOLOGY AND ENVIRONMENTAL HEALTH HAZARDS 

RONALD W. ESTABROOK, University of Texas Medical School, Dallas, 
Texas, Chairman 

THEODORE CAIRNS, Greenville, Delaware 

VICTOR COHN, George Washington University Medical Center, Washington, 
D.C. 

JOHN W. DRAKE, National Institute of Environmental Health Sciences, 
Research Triangle Park, North Carolina 

A. MYRICK FREEMAN, Bowdoin College, Brunswick, Maine 
RICHARD HALL, McCormick & Company, Hunt Valley, Maryland 

RONALD W. HART, National Center for Toxicological Research, Jefferson, 
Arkansas 

PHILIP LANDRIGAN, National Institute of Occupational Safety and 
Health, Cincinnati, Ohio 

MICHAEL LIEBERMAN, Washington University School of Medicine, St. 
Louis, Missouri 

BRIAN MacMAHON, Harvard School of Public Health, Boston, Massachusetts 
RICHARD MERRILL, University of Virginia, Charlottesville, Virginia 
ROBERT A. NEAL, Vanderbilt University, Nashville, Tennessee 
IAN NISBET, Massachusetts Audubon Society, Lincoln, Massachusetts 
CHARLES R. SCHUSTER, JR., University of Chicago, Chicago, Illinois 

GERALD WOGAN, Massachusetts Institute of Technology, Cambridge, 
Massachusetts 



ROBERT G. TARDIFF, National Research Council, Washington, D.C., 
Executive Director 



IV 



ACKNOWLEDGMENTS 



This document is the result of individual and coordinated efforts 
by the members of the Committee on Aldehydes. Although, as detailed 
below, individual members were responsible for specific sections, the 
entire report was reviewed by the full Committee. The summary 
(Chapter 2) and the recommendations (Chapter 3) represent a consensus 
of the Committee members. 

The introduction (Chapter 1) was prepared by the Chairman, Dr. 
Jack G. Calvert. Chapter 4, on the properties, production, and uses 
of the aldehydes, was prepared by Dr. Lyle F. Albright, Dr. Calvert, 
and staff; the Appendix, which contains details on many specific 
aldehydes, was prepared by staff. Chapter 5, on sources and 
concentrations, was a joint effort of Dr. Calvert, Dr. Albright, Dr. 
Eileen Brennan, Dr. Craig D. Hollowell, and Dr. David H. W. Liu, 
assisted by Dr. William R. Mabey. Chapter 6, on measurement methods, 
was written by Dr. Hollowell, assisted by his associate. Dr. Robert R. 
Miksch, and by Dr. Brennan and Dr. Liu. Dr. Stuart M. Brooks and Dr. 
Charles F. Reinhardt prepared Chapter 7, on health effects of 
formaldehyde, and Chapter 8, on health effects of some other 
aldehydes, with the assistance of Dr. Francis N. Marzulli, Mr. Richard 
C. Graham, and Dr. Joel Bender. Chapter 9, on the effects of 
aldehydes on vegetation, was written by Dr. Brennan, and Chapter 10, 
on the effects on aquatic organisms, was written by Dr. Liu. 

We acknowledge the contributions of Dr. Robert Frank, who served 
as chairman of the Committee in its formative period. 

Special recognition should be given to Dr. Albright, who chaired a 
subcommittee meeting at which resource information was presented by 
industrial representatives of the Formaldehyde Institute, the American 
Textile Manufacturers, Inc., the Manufactured Housing Institute, the 
Hardwood Plywood Manufacturers Association, and Aerolite SPE Corp. 
Special thanks should also be extended to Dr. Brooks, who chaired a 
subcommittee on the health effects of formaldehyde, which included Dr. 
Donald Proctor and Dr. Edward Emmett of Johns Hopkins University, who 
assisted in the evaluation of the health effects, and representatives 
of the Formaldehyde Institute, who made available resource information 
on the health effects. The efforts of Dr. John Clary and Mr. Kip 
Hewlett in organizing representation and the presentations made at 
these subcommittee meetings are greatly appreciated, as well as those 
of Dr. Leon Starr of the Celanese Corporation for his consultation and 
information resources furnished to the Committee. 

For providing resource material and other information, we express 
our gratitude to the following: 



v 



Dr. Eric R. Allen, Atmospnenc Sciences Research Center, 
State University of New York, Albany, New York 

Mr. Douglas Anthon, Lawrence-Berkeley Laboratory, University 
of California, Berkeley, California 

Dr. Charlotte Auerbach, University of Edinburgh, Edinburgh, 
Scotland 

Mr. W. L. Benning, Manufactured Housing Institute, Arlington, 
Virginia 

Mr. Charles A. Campbell, Aerolite SPE Corporation, Florence, 
Kentucky 

Dr. T. Cooke, Textile Research Institute, Princeton, New 
Jersey 

Mr. Maynard Curry, U.S. Department of Housing and Urban 
Development, Washington, D.C. 

Dr. John W. Drake, National Institute of Environmental Health 
Sciences, Research Triangle Park, North Carolina 

Dr. Julius Fabricant, New York State College of Veterinary 
Medicine, Ithaca, New York 

Ms. Mary Leah Fanning, Lawrence-Berkeley Laboratory, 
University of California, Berkeley, California 

Mr. Robert B. Faoro, U.S. Environmental Protection Agency, 
Research Triangle Park, North Carolina 

Mr. R. David Flesh, Del Green Associates, Foster City, 
California 

Dr. Alfred L. Frechette, Massachusetts State Department of 
Public Health, Boston, Massachusetts 

Dr. A. Myrick Freeman II, Department of Economics, Bowdoin 
College, Brunswick, Maine 

Mr. Ernest Freeman, Department of Energy, Washington, D.C. 

Dr. Thomas E. Graedel, Bell Laboratories, Murray Hill, New 
Jersey 

Mr. Serge Gratch, Ford Motor Company, Dearborn, Michigan 
Mr. William Groah, Hardwood Plywood Manufacturers 

Association, Arlington, Virginia 

Dr. Daniel Grosjean, Environmental Research and Technology, 

Inc., West Lake Village, California 

Mr. Jan Heuss, General Motors Research Laboratory, Warren, 
Michigan 

Mr. Richard C. Holmquist, American Mining Congress, 
Washington, D.C. 

Dr. Nelson S. irey, Armed Forces Institute of Pathology. 
Washington, D.C. 

Dr. Howard Johnson, SRI International, Menlo Park, California 



Dr. Philip Landrigan, National institute for Occupational 
Safety and Health, Cincinnati, Ohio P^ionai 

Dr. Charlotte R. Lindley, Department of Chemistry, Ohio State 
University, Columbus, Ohio 

Dr. Gunnar Lundqvist, Arhus University, Arhus, Denmark 



VI 



Dr. Geoffrey Meadows, E. I. du Pont de Nemours and Company, 
Wilmington, Delaware 

Mr. Andrew Micula, New Jersey Department of Environment 
Protection, Trenton, New Jersey 

Dr. Dominick J. Mormile, Consolidated Edison, New York, New 
York 

Mr. Charles Morschauset, National Particle Board Association, 
Silver Spring, Maryland 

Dr. Demetrios J. Moschandreas, GEOMET Technologies, Inc., 
Gaithersburg, Maryland 

Mr. John F. Murray, Formaldehyde Institute, Scarsdale, New 
York 

Ms. Laura A. Oatman, Minnesota Department of Health, 
Minneapolis, Minnesota 

Mr. Edward Owens, Aberdeen Proving Grounds, Maryland 

Mr. James Paine, Texas Air Control Board, Austin, Texas 

Dr. G. J. Piet, National Institute for Water Supply, 
Voorburg, The Netherlands 

Dr. James M. Ramey, Celanese Corporation, New York, New York 

Dr. Yuko Sasaki, Tokyo Metropolitan Research Institute for 
Environmental Protection, Tokyo, Japan 

Dr. Eugene N. Skiest, Borden, Inc., Columbus, Ohio 

Dr. Ronald J. Spanggord, SRI International, Menlo Park, 
California 

Dr. Karl J. Springer, Southwest Research Institute, 
San Antonio, Texas 

Dr. Edgar R. Stevens, California Statewide Air Pollution 
Research Center, Riverside, California 

Mr. William Stockwell, Department of Chemistry, Ohio State 
University, Columbus, Ohio 

Mr. John G. Tritsch, American Textile Manufacturers 
Institute, Washington, D.C. 

Dr. Michael P. Walsh, U.S. Environmental Protection Agency, 

Washington, D.C. 

Mr. Frank Walter, Manufactured Housing Institute, 
Arlington, Virginia 

Mr. Ralph C. Wands, Mitre Corporation, McLean, Virginia 

Dr. Jonas Weiss, CIBA-GEIGY Corporation, Ardsley, New York 

Dr. Rather me W. Wilson, Pacific Environmental Services, 
Santa Monica, California 

Ms. Mary Ann Woodbury, Wisconsin State Department of Health 
and Social Services, Madison, Wisconsin 

Free use was made of the resources of the Toxicology Information 
Center of the Board on Toxicology and Environmental Health Hazards, 
National Research Council; the National Library of Medicine; the 
National Agricultural Library; the Library of Congress; and the Air 
Pollution Technical Information Center of the Environmental Protection 
Agency. Also acknowledged is the assistance given to the Committee by 
the National Academy of Sciences Library and various other units of 
the National Research Council. 

VI 1 



CONTENTS 



1 Introduction 1 

2 Summary 3 

3 Recommendations 11 

4 Commercial Production, Properties, and Uses of 

the Aldehydes 20 

5 Aldehyde Concentrations, Emission, and Environmental 
Generation and Transformation Reactions 36 

6 Analytical Methods for the Determination of 

Aldehydes 132 

7 Health Effects of Formaldehyde 175 

8 Health Effects of Some Other Aldehydes 221 

9 Effects of Aldehydes on Vegetation 256 

10 Effects of Aldehydes on Aquatic Organisms 276 
Appendix: Properties, Uses, and Synonyms of Selected Aldehydes 289 



ix 



CHAPTER 1 
INTRODUCTION 



This report was prepared at the request of the Environmental 
Protection Agency (EPA) by the Committee on Aldehydes, which was 
appointed by the National Research Council in the Board on Toxicology 
and Environmental Health Hazards, Assembly of Life Sciences. The 
Clean Air Act requires that from time to time the Administrator of EPA 
evaluate the need for air-quality criteria on pollutants that may have 
adverse effects on man or the environment. This report is to be used 
by EPA in assessing the need for such criteria on some of the 
aldehydes. It is intended to identify and characterize the more 
important aldehydes that pollute the environment, the sources of their 
emission, their concentrations, their transformation and transport, 
their effects on the health of animals and humans, and their effects 
on the aquatic and terrestrial environments. It is not intended to 
recommend concentrations of polluting aldehydes for use in developing 
regulations, but rather to evaluate the available data for EPA to use 
in judging the need for regulatory strategies to control aldehyde 
pollution. It is hoped that wide dissemination of this report will 
inform physicians and other health professionals about the health 
effects of aldehydes and how they may be encountered at hazardous 
concentrations in the environment. 

The Committee had hoped to address the economics of the options 
for abatement of aldehyde pollution, and it chose formaldehyde as the 
model of the aldehydes because of its perceived importance and because 
it is used in a wide variety of products. Techniques for abating 
formaldehyde emission are still evolving and being tested; their value 
has not been proved, and their costs and cost-benefit relationships 
are not known. Therefore, on the grounds of a lack of usable 
information, the economic analysis of control options was abandoned. 

Chapters 2 and 3 summarize the Committee's findings and set forth 
the Committee's recommendations, respectively. 

Chapter 4 describes commercial methods of production of the 
aldehydes and their uses. Chapter 5 reviews the reported atmospheric 
concentrations of the aldehydes in clean and urban environments, in 
indoor environments, and in surface and drinking waters; considers the 
sources of direct emission from industrial operation, combustion, 
consumer products, natural vegetation, and indoor environments; and 
evaluates current theories of the mechanism of aldehyde generation in 
the atmosphere, the aldehyde removal processes that operate in the 



environment, and the secondary effects of aldehydes in the chemistry 
of the polluted atmosphere. Chapter 6 reviews and evaluates the 
methods of analysis of formaldehyde and selected higher aldehydes and 
methods of sampling and of preparing standards. 

Formaldehyde has prominence throughout the report, because it is 
ubiquitous, is used in very large quantities, and is mutagenic in 
microorganisms and insects and carcinogenic in Fischer 344 rats, in 
Chapter 7, the health effects of formaldehyde in terrestrial animals 
and humans are discussed in detail; Chapter 8 covers the health 
effects of selected other aldehydes; Chapter 9 discusses the effects 
of selected aldehydes on vegetation; and Chapter 10 discusses the 
effects of some aldehydes on aquatic organisms. 

The Appendix summarizes in tabular form several of the important 
physical and chemical properties of a number of the aldehydes that 
have been found in the environment. This compilation is not intended 
to be exhaustive, nor should the importance of these aldehydes be 
inferred from their listing. 

This report cites references available to the Committee up to July 
1, 1980, with one exception: a study that was made public in November 
1980 and provided more recent information on an earlier study that was 
cited. The work of the Committee from July 1, 1980, onward was 
devoted to an analysis of the information in hand. Thus, scientific 
papers and analyses published after that date were not considered. 



CHAPTER 2 
SUMMARY 



Although many of the aldehydes are minor components of the natural 
environment, we now recognize the potential impact of some of them on 
the urban and indoor environments. Thus, there is a need to study 
their sources r concentrations, transport, and transformations and 
their effects on various environmental and biologic systems. 



PRODUCTION, USES, AND PROPERTIES OF THE ALDEHYDES 

The aldehydes are produced at the rate of several billion pounds 
per year in the United States. Formaldehyde is the most important 
aldehyde produced commercially; about 9 billion pounds per year of the 
37-50% aqueous solution, called formalin, are prepared. The 
production methods depend on the catalytic oxidation of methanol . 
About half the formaldehyde produced is used in the preparation of 
urea-formaldehyde and phenol-formaldehyde resins, which are applied in 
the manufacture of plywood, particleboard, foam insulation, etc. 
Another 25% is used to make other high polymers and resins. Its use 
is so diversified that there is a potential for exposure in a number 
of occupational, environmental, and consumer settings. About 1 
billion pounds of acetaldehyde are prepared commercially each year in 
the United States, about 80% of it by the catalytic oxidation of 
ethylene in aqueous solution. This aldehyde is the major raw material 
for the preparation of acetic acid and other important chemicals. 
Smaller amounts of acrolein and the higher-molecular-weight aldehydes 
are prepared commercially. The simplest aldehydes are volatile 
compounds with characteristic pungent odors. These compounds are 
readily oxidized and polymerized. 



ALDEHYDE EMISSION, CONCENTRATIONS, AND ATMOSPHERIC TRANSFORMATIONS 

The aldehydes are introduced into the atmosphere through a variety 
of natural processes and as a result of human activity. In the 
atmosphere, they are generated through the photooxidation of both 
naturally occurring and anthropogenic hydrocarbons. They are injected 
directly into the atmosphere in the exhaust gases from automobiles and 
nther equipment in which hydrocarbon fuels are incompletely burned. 



Aldehydes are emitted from various industrial and manufacturing 
operations, power plants that burn fossil fuels, forest fires and open 
burning of wastes, and vegetation. 

The accumulation of aldehydes in the atmosphere as a result of 
their direct release and photochemical generation is counterbalanced 
by several important removal paths. The aldehydes absorb the 
ultraviolet component of sunlight and decay into free-radical and 
molecular products. They also react rapidly with the highly reactive 
free radicals, largely the hydroxy free radical, present in the 
sunlight-irradiated atmosphere. Because of the high water solubility 
of formaldehyde and the other low-molecular-weight aldehydes, one 
expects the efficient transfer of aldehydes into rainwater, the 
oceans, and other surface waters. The high reactivity of the 
aldehydes leads to rather short half-lives, of around a few hours, in 
the sunlight-irradiated lower atmosphere. Thus, the atmospheric 
transport of the aldehydes over long distances is probably a less 
likely source in remote areas than their local generation from 
transported, longer-lived precursors, such as the less reactive 
hydrocarbons. The lifetime of formaldehyde in aqueous media may be 
somewhat greater than that of the gas-phase species, because the 
hydrated form of formaldehyde, which dominates in these conditions, 
does not absorb sunlight appreciably. The higher aldehydes do not 
have this protective mechanism, because of the lower degree of 
hydration. Microorganisms appear to play an important role in the 
degradation process, which may take 30-72 h in these cases (in natural 
conditions) . 

Many people may be exposed to aldehydes at high concentrations 
(i.e., above ambient) in the indoor environment of the home. Sources 
of aldehydes in conventional residential buildings and mobile homes 
include building materials, insulation, combustion appliances, tobacco 
smoke, and various consumer products. These sources emit aldehydes in 
substantial amounts; as a result, indoor aldehyde concentrations 
almost always exceed outdoor concentrations. 

In any environment, the ambient concentrations of aldehydes depend 
on the rates of the formation and removal reactions. In a clean 
environment, aldehyde concentrations at ground level are commonly 
0.0005-0.002 ppm (0.6-2.5 pg/m 3 ) . In ambient urban air, the 
concentrations are much higher, usually an hourly average of 
0.004-0.05 ppm (5-61 pg/nr*) during the daylight hours. 
Formaldehyde is the dominant aldehyde present, usually constituting 
30-75% of the total aldehydes. Acetaldehyde may be present at about 
60% of the formaldehyde concentration, with smaller amounts of the 
higher aliphatic aldehydes. Acrolein may be present at 10-25% of the 
formaldehyde concentration, and the aromatic aldehydes usually make up 
only a few percent of the total aldehydes . In most indoor 
environments, 24-h average formaldehyde concentrations of 0.05-0.2 ppm 
(61-246 yg/nr) are not uncommon today. However, in some indoor 
environments concentrations of a few parts per million or higher have 
been reported. In the aquatic environment, aldehyde concentrations 
are generally less than 1 ppb. Concentrations of some aldehydes in 
the parts-per-million range have been reported in industrial effluents, 



The aldehydes affect the chemistry of the chemically polluted 
atmosphere in a variety of complex ways. An increased aldehyde 
concentration decreases the induction period for the generation of the 
products of photochemical smog and increases the maximal concentration 
of ozone. The aldehydes other than formaldehyde are precursors of an 
important class of secondary pollutants, the peroxyacylnitrates and 
peroxybenzoylnitrates, which have been identified as highly active eye 
irritants and plant-damaging agents. Through several atmospheric 
reaction pathways, formaldehyde may be converted to formic acid. The 
interaction of formaldehyde and hydrogen chloride can lead to 
chloromethylethers, which are potential carcinogens, although current 
knowledge (which may be incomplete) indicates that the concentrations 
formed in the atmosphere at ambient concentrations of reactants would 
be so low that there is little probability of an impact on health. 
Thus, formaldehyde affects the quality of the ambient air not only 
directly, but also indirectly by way of its chemical transformations, 
involvement in photochemical smog reactions, and interaction in 
combination with other pollutants. 



ANALYTICAL METHODS FOR THE DETERMINATION OF THE ALDEHYDES 

The techniques for quantitative analysis of the aldehydes have not 
been investigated adequately with respect to the necessary 
reliability, sensitivity, and specificity. Accurate analysis for the 
aldehydes in the environment is essential to an assessment of their 
qualitative and quantitative influence on the environment and on the 
health of those exposed. The solution-phase spectrophotometnc 
methods are the most commonly used analytical techniques. Although 
the individual aldehydes can be selectively measured with methods now 
available, the methods require improvement and standardization. 
Measurements of "total" aldehyde provide little help in the assessment 
of the impact of these compounds in the environment, because the 
variation in toxicity among the individual aldehydes is large for 
example, the current Occupational Safety and Health Administration 
standards for exposure to acetaldehyde, formaldehyde, and acrolein are 
200, 3, and 0.1 ppm, respectively. It is recognized that future 
analytical methods for aldehydes should provide an accurate 
determination of the specific aldehydes present in a given sample. 
Several methods appear to offer this potential. Many involve the 
derivatization of the aldehydes and the use of gas- or 
liquid-chromatographic separations and analysis. Further development 
is necessary to establish these methods for general use. 



HEALTH EFFECTS OF FORMALDEHYDE 

Formaldehyde has been the subject of numerous complaints regarding 
irritation of the eyes and respiratory tract, nausea, headache, 
tiredness, and thirst. These symptoms have been reported mainly by 
residents of homes in which formaldehyde has been identified as a 



result of off-gassing from urea-formaldehyde foam insulation, 
particleboard, or plywood. Studies of employees exposed to 
formaldehyde in the workplace and in controlled exposures have further 
indicated that the skin, eyes, and respiratory tract are the target 
organs affected. 

Aqueous solutions of formaldehyde are damaging to the eye and 
irritating to the skin on direct contact. Repeated exposure to dilute 
solutions may lead to allergic contact dermatitis. There are some 
documented cases showing that formaldehyde is a cause of skin 
responses in sensitized persons using cosmetic formulations that 
contain formaldehyde at very low concentrations (0.01%). There are 
few documented cases showing that formaldehyde is a cause of 
hypersensitivity in persons with bronchial asthma; more commonly, 
asthma is aggravated by the irritating properties of formaldehyde. 
Systemic poisoning from ingestion is uncommon, because the irritancy 
of formaldehyde makes ingestion unlikely. 

Numerous studies have shown that formaldehyde is irritating to the 
eyes and upper respiratory tract of laboratory animals. Preliminary 
results of a chronic-inhalation study sponsored by the Chemical 
Industry Institute of Toxicology (CUT) have shown that formaldehyde 
induces nasal cancer in Fischer 344 rats exposed at 15 ppm 6 h/d, 5 
d/wk for 18 mo, but not yet in B6C3F1 mice similarly exposed. 
(However, the CUT reported at the Formaldehyde Symposium on November 
20-21, 1980, in Raleigh, N.C., that nasal cancer had been observed in 
rats exposed at 6 ppm for 24 mo and in mice exposed at 15 ppm for 24 
mo.) Fischer 344 rats have also shown dose-related histologic changes 
(epithelial dysplasia and squamous metaplasia) of the nasal mucosa 
after exposure at 2, 6, and 15 ppm. Although there is no evidence of 
the carcinogenicity of formaldehyde in humans, the results of these 
studies showing carcinogenicity in rats require that serious attention 
be given to an evaluation of the carcinogenic potential of 
formaldehyde in exposed humans. Formaldehyde has not altered 
reproduction or shown evidence of teratogenicity in animals, but it 
has exhibited mutagenic activity in several nonmammalian animal or 
cell systems. The human mutagenic and teratogenic potential of 
formaldehyde is not known. 

The presence of environmental agents other than formaldehyde, 
smoking history, variability of health status, age, and genetic 
predisposition may modify responses to formaldehyde. These factors 
have not been adequately evaluated; that makes it difficult to assess 
accurately the health risks attributable solely to formaldehyde. 
However, the complaints of residents of homes with formaldehyde- 
containing products have been shown to be similar to complaints made 
by persons studied in the laboratory at similar formaldehyde 
concentrations; hence, these subjective complaints about health 
effects may be related to formaldehyde exposure in the home, although 
the presence of other pollutants causing the same symptoms must not be 
overlooked. Accordingly, a substantial proportion of the U.S. 
population may be likely to develop symptoms of irritation, if exposed 
to formaldehyde at low concentrations. As discussed in detail in 
Chapter 7, on the basis of laboratory tests and various kinds of 



population surveys, it nas been estimated that some 10-20% of the 
general population may be susceptible to the irritant effects of 
formaldehyde at low concentrations. For example, most people report 
mild eye, nose, and throat irritation at a concentration of 1 ppm, 
whereas some note symptoms at concentrations below 0.5 ppm. In 
laboratory investigations, under controlled conditions, responses have 
been reported at formaldehyde concentrations as low as 0.01 ppm when 
formaldehyde was present in combination with other air pollutants. 
Low concentrations may also cause bronchoconstriction and asthmatic 
symptoms in some susceptible persons. The specific effects of 
continuous exposure on other susceptible populations such as infants, 
young children, pregnant women, and the infirm are not known. The 
exact numbers of susceptible people residing in environments where 
formaldehyde concentrations could produce adverse responses cannot be 
determined. Millions of persons live in mobile homes or conventional 
homes that have particleboard, plywood, or urea-formaldehyde foam 
(resin) insulation. On the basis of monitoring of a fairly large 
number of houses in these categories, significant formaldehyde 
concentrations were detected in several hundred American homes, and 
these concentrations were caused in large part by outgassing from 
these building materials. Much of this monitoring was done as a 
direct result of customer complaints. Yet other homes in these 
categories, including some with customer complaints, demonstrated 
formaldehyde concentrations basically comparable with those in homes 
that did not contain such building materials. On the basis of 
estimates of susceptibility of the general population to formaldehyde, 
it may be anticipated that a substantial number of persons are at risk 
of adverse health effects (upper and lower respiratory tract effects, 
eye irritation, etc.). Because of the incompleteness of the data, no 
conclusions can be drawn about the carcinogenic risks to humans 
exposed to formaldehyde. 



HEALTH EFFECTS OF SOME OTHER ALDEHYDES 

The principal effect of human exposure to other aldehydes, 
particularly acrolein and acetaldehyde , at low concentrations, is 
irritation of the eyes, skin, and mucous membranes of the upper 
respiratory tract. It has been demonstrated that several 
environmental irritants are ciliotoxic and mucus-coagulating agents. 
The aldehydes which include acetaldehyde, propionaldehyde, and 
acrolein may thus facilitate the uptake of other atmospheric 
contaminants by the bronchial epithelium. 

Acetaldehyde, the least toxic of the atmospheric aldehydes, is 
slightly toxic when administered orally. The effect of direct contact 
with liquid acetaldehyde has not been studied, but industrial 
experience suggests that there is little hazard. Repeated-exposure 
studies indicated that significant toxic effects appear only at high 
concentrations. An 18-wk inhalation study in hamsters showed no 
adverse effects at 390 ppm (7.0 x 10 5 yg/m 3 ) . Acetaldehyde is 
thought to be an important contributor to the health 



effects of cigarette smoke. It does not appear to have substantial 
mutagenic or carcinogenic effects, but more extensive studies are 
required to test this possibility. A major source of acetaldehyde in 
the body is the metabolism of ethanol. Acetaldehyde has shown 
embryotoxic and teratogenic effects in mice similar to those produced 
by ethanol. 

Acrolein is the most acutely toxic of the atmospheric aldehydes. 
It is highly toxic by the oral and skin-absorption routes. It 
produces severe injury on contact with the skin and eyes. Inhalation 
of acrolein vapors by cats and rats produces severe eye and 
respiratory tract irritation at concentrations as low as 12 ppm (2.8 x 
10 4 yg/m 3 ) and death in rats after 4-h exposure at 8 ppm (1.8 x 
10 yg/m ) ; its vapors produced little or no effect at up to 0.2 
ppm (458 ym/nr) . Exposed animals appear to develop tolerance 
within a few weeks. Higher concentrations cause species- and 
dose-dependent histopathologic changes in both the upper and the lower 
respiratory tract. Although acrolein has been shown to be mutagenic 
in nonmammalian systems, it has not been shown to be carcinogenic in 
hamsters. In a single study, it was found not to be embryotoxic in 
rats. 

Crotonaldehyde produces symptoms similar to those described for 
acrolein. Eye and respiratory tract irritation is seen with 
propionaldehyde, n-butyraldehyde , isobutyraldehyde, and chloral. 
Chloral is unique, in that its inhalation toxicity puts it in the 
highly toxic category for acute exposures. Other high-molecular- 
weight aldehydes such as chloroacetaldehyde, valeraldehyde, furfural, 
the butyr aldehydes , glyoxal, malonaldehyde, benzaldehyde, 
synapaldehyde, and the naturally occurring aldehydes appear to be 
less toxic than formaldehyde and acrolein, although studies of these 
compounds are incomplete. 



EFFECTS OF ALDEHYDES ON VEGETATION 

Several studies concerning aldehyde phytotoxicity have been 
reported. Manifestations of injury include visible symptoms on 
foliage and effects on growth, photosynthesis, respiration, 
transpiration, seed germination, and pollen-tube elongation. Early 
California studies demonstrated that exposure of five smog-sensitive 
field crops to formaldehyde vapors (uncontrolled fumigations at 2 ppm, 
or 2.5 x 10 yg/m 3 , for 2 h) caused no noticeable effect. Some 
doses of acrolein (0.1 ppm, or 229 yg/m 3 , for 9 h) and 
trichloroacetaldehyde (0.8 ppm, or 4.8 x 10 3 yg/m 3 , for 4 h) 
induced smog-like damage to alfalfa leaves, but higher doses of 
acrolein (0.6 ppm, or 1.4 x 10 3 yg/m 3 , for 3 h and 1.2 ppm, or 
2.8 x 10 3 yg/m 3 , for 4.5 h) caused injury in spinach, endive, 
and beet leaves unlike that caused by smog. Visible injury in pinto 
bean leaves occurred after 70 mm of exposure to acrolein at 2.0 ppm 
(4.6 x 10 3 yg/m 3 ). Products of the irradiated aldehydes in air 
have also been tested, in a 4-h exposure at 0.5 ppm. Irradiated 
formaldehyde and acetaldehyde caused no damage 



to petunias and pinto beans, but propionaldehyde and butyraldehyae 
caused a glazing of the lower leaf surface of both plants. 

Slightly reduced rates of photosynthesis and respiration were 
measured when an alga (Euglena gracilis) was exposed to formaldehyde 
at 0.075 ppm (92 yg/m 3 ) for 1 h, and photosynthesis was 
significantly reduced after exposure to propionaldehyde at 0.1 ppm 
(123 yg/m 3 ) for 1 h. In fasted cells, the effects were minimized. 

A rather large concentration (10~^ M, or 24 ppm) of a single 
higher aldehyde (trans-2-hexenal, pentanal, hexanal, heptanal, 
octanal, or nonanal) decreased the transpiration rate in wheat 
seedlings to less than that observed in complete darkness. 

Aldehydes have been observed to inhibit pollen-tube elongation in 
lily. Although exposure to formaldehyde at 0.37 ppm (454 yg/m 3 ) 
for 1-2 h had no effect, a 5-h exposure at this concentration resulted 
in inhibition. Acrolein was more injurious, causing a 40% decrease in 
tube length when the lily was exposed at 0.4 ppm (917 yg/m ) for 
2 h. 

Various other detrimental effects of aldehydes on plants have been 
observed. For example, oat, wheat, corn, barley, tomato, bean, 
lettuce, and radish showed a marked reduction in seedling growth and 
seed germination after exposure to polymer -treated woods. Presumably, 
the formaldehyde vapors that escaped from the wood were responsible. 

On the basis of available information, one might expect to find 
some response of sensitive plants to aldehydes in ambient air. This 
will probably be seen first in the fast-growing herbaceous plants, 
rather than the woody, slow-growing species. 

Present data suggest that aldehyde phytotoxicity itself is a minor 
pollution problem. However, in combination with the more common air 
pollutants, nitrogen dioxide and sulfur dioxide, phytotoxicity may be 
increased. The aldehydes may also contribute to the generation of the 
phytotoxic oxidants ozone and peroxyacyl nitrates, or PAN. Thus, the 
vegetation problem could become more serious if aldehyde and other 
pollutant concentrations rise substantially. 



EFFECTS OF ALDEHYDES ON AQUATIC ORGANISMS 

Thirty-six aldehydes have been identified in water, including 
industrial and sewage-treatment plant discharges, surface waters, and 
drinking water. Although the concentrations of many of these 
aldehydes in water are unknown, the concentrations of 22 in natural 
bodies of water or in drinking water have been determined to be less 
than 0.012 mg/L. The concentrations of five aldehydes that have been 
identified in aqueous waste discharges range up to 0.24 mg/L. 
Although the water-sampling sites have been limited, they are probably 
representative, and the results show that in general the aldehyde 
concentrations in the aquatic environment are relatively low. 

Only seven of the 36 aldehydes (acrolein, formaldehyde, 
acetaldehyde, fur fur aldehyde, crotonaldehyde , propionaldehyde, and 
vanillin) have been fully evaluated for acute toxicity in at least two 
aquatic species. The lowest reported median lethal concentrations 



10 

for various exposure times and organisms range from about 
0.05 mg/L for acrolein to 112 mg/L for vanillin and 130 mg/L for 
propionaldehyde . Acute-toxicity screening tests on 13 aldehydes 
showed most to be nontoxic to fish at 5 ppm and all to be nontoxic at 
1 ppm. Only acrolein has been evaluated for chronic effects. From 
its evaluation of the data, the Environmental Protection Agency has 
determined the chronic LC5Q values of acrolein to be 0.024 mg/L for 
the cladoceran Daphnia raagna and 0.021 mg/L for the fathead minnow, 
Pimephales promelas. 

On the basis of the method that uses calculated octanol-water 
partition coefficients (P) , most of the aldehydes will probably not 
bioaccumulate substantially. However, six of them (capraldehyde, 
caprylaldehyde , 3 , 5-di-tert-butyl-4-hydroxybenzaldehyde , 
mesitaldehyde, nonylaldehyde , and undecylaldehyde) have log P values 
of at least 3.0; this suggests that they could accumulate appreciably 
in the tissues of aquatic organisms in the absence of rapid removal 
reactions. 

Although little is known about the persistence of aldehydes in 
aqueous systems, it appears that a variety of aliphatic and aromatic 
aldehydes including formaldehyde, acrolein, benzaldehyde, 
salicylaldehyde, syringaldehyde, and vanillin can be biodegraded 
relatively rapidly. 

The little information available now suggests that aldehydes 
(except acrolein) have low to moderate toxicity in aquatic organisms. 
We can conclude that the concentrations of aldehydes found in water 
are in most cases lower than those shown to have toxic effects in 
toxicity tests. There is some evidence that aldehydes do not persist 
for long periods in water that contains microorganisms; hence, the 
probability of occurrence of long-term effects appears to be low. 
However, many of the aldehydes have not yet been evaluated for 
toxicity in aquatic organisms, so our conclusion must be regarded as 
tentative. 



CHAPTER 3 
RECOMMENDATIONS 



This document reviews the present knowledge on formaldehyde and 
some important higher aldehydes with respect to their production, 
properties, ambient and indoor concentrations, potential sources and 
sinks, and effects on humans, aquatic and terrestrial animals, and 
plants. The Committee recognizes that the first priority in its 
consideration is the determination of the effects of specific 
aldehydes on human health. However, serious deficiencies in its 
current knowledge prevent the immediate attainment of this primary 
goal. It is necessary to have unambiguous methods of analysis of 
specific aldehydes, comprehensive emission inventories, atmospheric 
generation and destruction rates, and measured concentrations of the 
individual aldehydes in indoor and outdoor environments to which human 
populations are exposed, as well as definitive health studies related 
to the specific aldehydes. This chapter identifies the missing 
scientific information that is needed if sound strategies for the 
control or abatement of aldehyde pollution are to be formulated and 
offers specific recommendations for obtaining the needed information. 
The Committee has not studied the direct or indirect economic impact 
of the implementation of these recommendations. The order of 
presentation reflects a suggested priority of the needed studies in 
each section, although we believe that all the recommendations deserve 
serious consideration by those concerned with the effects of the 
aldehydes on humans and the environment. 



CHEMISTRY OF THE ALDEHYDES IN THE ENVIRONMENT 

Many aspects of the sources, sinks, and transformation mechanisms 
of the aldehydes in the atmosphere, in outdoor and indoor 
environments, on the land, and in the surface waters remain 
ill-defined. A variety of further studies are required to permit the 
development of useful models of the potential ambient environmental 
and indoor concentrations of the aldehydes and their concentrations in 
natural surface and ground waters to which humans, terrestrial 
animals, aquatic organisms, and plant life will be exposed. Present 
information on the aldehyde exposure of the human population is at 
best incomplete. 

11 



12 

Tnere are some serious deficiencies in our present knowledge of 
indoor aldehyde sources and concentrations. In particular, studies on 
the following issues are required, to allow a careful assessment of 
the indoor-aldehyde problem: studies of building materials 
(particleboard, plywood, urea-formaldhyde foam insulation, etc.) from 
the point of view of their aldehyde emission rates and intervening 
factors (such as ventilation rate, temperature, and humidity); studies 
to measure the emission of other indoor sources of formaldehyde, such 
as gas-fired appliances, tobacco smoke, consumer products, and outdoor 
air; studies on the type and effectiveness of various schemes to 
reduce the indoor concentration of aldehydes; and monitoring studies 
that use reliable analytical techniques to assess aldehyde 
concentrations in a broad spectrum of occupied indoor environments. 

Manufacturers of indoor plywood and particleboard should be able 
in the future to produce materials that have substantially lower 
emission of formaldehyde; however, it is not clear whether completely 
satisfactory solutions to the problem are possible. The Committee 
recommends that manufacturers continue work on the following promising 
approaches: Somewhat reduced amounts of formaldehyde should be used 
in preparation of the resins; improved polymerization recipes and 
better control of reaction conditions may result in less unreacted 
formaldehyde in the resin product. Techniques should be developed to 
remove excess or unreacted formaldehyde from the final product; for 
example, controlled heating and extended storage of the product before 
sale to the consumer will certainly promote escape of formaldehyde 
from the product. The surfaces of the final products should be sealed 
to minimize the escape of unreacted formaldehyde to the atmosphere; a 
specific sealing agent has recently been reported to reduce 
formaldehyde escape by about 70%, and paints and varnishes would 
presumably have some similar effect, but information on their use has 
not been reported; such sealers may also minimize moisture absorption 
and subsequent hydrolysis reactions. If suitable solutions to the 
formaldehyde problem of urea- formaldehyde resins cannot be obtained, 
the alternative is to select other resins , such as phenol- 
formaldehyde, melamine-formaldehyde, or epoxy; it is recognized that 
cost, appearance of the final consumer product, and somewhat poorer 
physical properties may militate against some or all of these 
alternative resins, and other building materials may be required as 
replacements for the present types of plywood or particleboard. 

The combustion of fossil fuels including natural gas, gasoline, 
diesel fuel, oil, and coal and of wood, trash, etc., produces exhaust 
gases that contain both aldehydes and unburned hydrocarbons. Unburned 
hydrocarbons are transformed in part to aldehydes as intermediate 
compounds in atmospheric oxidation reactions. Ambient concentrations 
of these compounds in polluted urban areas are increased appreciably 
by exhausts from transportation vehicles. The controls used on new 
vehicles appear to offer reasonable regulation of both hydrocarbons 
and aldehydes. However, careful continued study of the emission from 
all internal-combustion engines is required as fuel composition and 
engine design are altered in the years ahead. In view of the high 
probability of the increased use of gasohol and methanol fuels and the 



13 

expectation that formaldehyde and acetaldehyde are products of the 
incomplete combustion of these fuels, aldehyde emission from the 
exhaust of new and old vehicles of all kinds should be monitored 
regularly as these fuels increase in use. The aromatic-hydrocarbon 
content in liquid fuels, such as gasoline, may be of concern, for at 
least two reasons: first, there will be direct emission or 
vaporization losses, and, second, these compounds produce aromatic 
aldehydes in their atmospheric photooxidation. Benzaldehyde, the 
methylbenzaldehydes, and other aromatic aldehydes are precursors of 
the highly irritating peroxybenzoylnitrates, which would be formed in 
the atmospheric photooxidation reactions expected to occur. Tfte 
increasing use of diesel fuels will cause somewhat new emission 
control problems. The emission of the higher aldehydes, as well as 
the common low-molecular-weight aldehydes, may be expected, and 
suitable controls may need to be investigated to address this 
potential problem. 

The search for synergistic effects involving the aldehydes must 
continue. Thus, there should be special research efforts to 
investigate the ambient concentrations of bis (chloromethyl) ether in 
regions of high formaldehyde and hydrogen chloride concentrations. 
Further quantitative work is required to delineate the thermodynamic 
and kinetic properties of the formaldehyde-hydrogen chloride- 
fa is (chloromethyl) ether system, to allow a quantitative assessment of 
the potential formation of the chloromethylether to which human 
populations may be commonly exposed. 

Outdoor air concentrations of formaldehyde, the higher aliphatic 
and aromatic aldehydes, and acrolein should be monitored in the air on 
a continuing basis in a large number of heavily populated, rural, and 
remote areas, so that a reasonable data base on ambient aldehyde 
concentrations can be established. 

The expected theoretical relation of the peroxyacylnitrates and 
peroxyarylnitrates and ozone to the precursor aldehydes should be 
tested in a continuing effort. Ambient concentrations of ozone and 
peroxyacetylnitrate and higher homologues should be measured at the 
same sampling sites used for the aldehyde determinations. Correlation 
checks will require continuous monitoring of nitrogen dioxide, nitric 
oxide, nonmethane hydrocarbons, carbon monoxide, methane, sulfur 
dioxide, and possibly other contaminants. 

Industrial-plant manufacture or use of aldehydes will always 
result in the release of some aldehydes to the environment. Although 
the present industrial control methods appear to be well conceived and 
efficient removal of aldehydes is theoretically possible, continued 
measurement of this emission is advised. This applies not only to 
plants preparing formaldehyde and acetaldehyde, the most important 
commercial aldehydes, but especially to the manufacture of the highly 
toxic aldehyde, acrolein. 

Installation of urea-formaldehyde foams as insulation material has 
often resulted in excessive formaldehyde emission. At least a 
substantial portion of the emission can be attributed to poor 
installation techniques or improper use of materials. It is 
recommended that companies supplying the materials develop improved 



14 

reactants, training procedures, and installation procedures for local 
contractors. Potential customers should also be made aware that 
formaldehyde will be emitted for some period after installation, even 
with the best combination of installation procedures and materials. 
Such emission to the atmosphere and the aquatic environment is not 
well characterized in most cases. 

The aldehydes in the aquatic and terrestrial environments are 
potential sources of human exposure. Thus, it is recommended that 
pollution of the aquatic and terrestrial environments be studied to 
determine the hazardous concentrations of aldehydes to which humans 
and other organisms are likely to be exposed. 



QUANTITATIVE ANALYSIS OF ALDEHYDES IN THE ENVIRONMENT 

The ultimate value of any research related to the environmental 
effects of the aldehydes depends on the reliability, reproducibility, 
and accuracy of the analytical data that demonstrate the nature and 
amount of the aldehydes. Although many analytical procedures have 
been used in previous aldehyde studies, there are substantial problems 
associated with most of those in use today. 

No technique common to the analysis of all aldehydes can yet be 
recommended. A series of more limited techniques that are widely 
used, generally for an individual aldehyde like formaldehyde, are 
discussed in Chapter 6. Very few of these are without fault in one or 
more respects: calibration, sampling procedure, or method of 
analysis. These limitations prevent their recommendation. Many of 
the techniques have common procedures, and hence common faults. 
Improved procedures for calibration, sampling, and analysis that are 
now recognized must be coupled to produce a series of refined, 
although still limited, techniques that can be recommended as standard 
measurement procedures and thus be applied immediately. However, 
emphasis should be on developing new techniques to secure the greatest 
benefit in the shortest time. 

Wet-chemical spectrophotometric methods of analysis are the most 
practical and best-established methods for determining aldehydes, and 
their continued use is recommended for the immediate future, with some 
stipulations. First, there must be recognition that the information 
provided by these methods is limited; they generally measure either an 
individual aldehyde or the aldehydes as a class without 
discrimination. The accurate assessment of specific aldehydes as 
environmental pollutants may require the application of several 
methods. Second, recommendation of these methods of analysis should 
not impede investigations of promising alternatives. Possible 
improvements such as increased sensitivity, decreased analysis time, 
or the simultaneous quantitative determination of several 
aldehydes should be actively sought. With these two stipulations, we 
recommend the seemingly optimal wet-chemical spectrophotometric 
methods for aldehydes, of which the most widely used for the 
determination of formaldehyde are based on chromotropic acid and 
pararosaniline reagents. However, there are serious problems with 



15 

methods that use chromotropic acid: determination of optimal analysis 
conditions, interfering substances, and lower sensitivity relative to 
alternative reagents. The pararosaniline method appears to be a 
suitable replacement for the chromotropic acid method. Its 
sensitivity is high, and interferences are minimal. Extensive testinc 
should be continued, to confirm its use as a standard method for the 
analysis of formaldehyde in air. For the near future, the 
acetylacetone method shows the greatest promise, by virtue of its 
greater sensitivity, and should be evaluated for use in the analysis 
of air. 

In view of the limitations of information obtained by measuring 
the total aldehyde content of mixtures that may have various ratios o 
aldehydes with substantially different toxicity, it is recommended 
that the methods of analysis for "total" aldehyde not be used in 
future studies involving atmospheric aldehydes. 

Techniques for the quantitative analysis of a large number of 
specific aldehydes in the environment are highly desirable for 
maximizing information. Such techniques probably will rely on 
gas-phase or liquid-phase chroma tography for separation. Because sue! 
techniques also rely on derivatization of the aldehydes, one possible 
approach would involve the use of passive monitors containing a 
derivatizing trapping agent in conjunction with a chromatographic 
separation method and analysis. 

Techniques that can provide real-time measurements at field 
sampling sites are extremely desirable. It may be possible to develo 
continuous monitors that use established wet-chemical spectrophoto- 
metric methods of analysis; this would require little chemical 
research, but considerable engineering development. A number of 
alternative direct spectroscopic measurement techniques have been use' 
in laboratory and atmospheric studies, but it is difficult to 
recommend these for a large number of sites without promise of future 
reduced cost and increased portability. However, it should be 
recognized that such direct techniques can provide analytical 
information based on characteristic spectral line structure and 
position; this allows an excellent check on possible unforeseen 
interferences that may be present in the less direct aqueous-phase 
spectrophotometric methods. 

There are two methods of analysis to be considered for measuring 
the highly toxic and environmentally important aldehyde, acrolein. 
The method using 4-hexylresorcinol is well established, and its 
continued use is recommended. Field mishaps may be minimized and 
sample stability improved by collection in a bisulfite solution. A 
second fluorimetric method using m-aminophenol shows promise and coul 
offer substantially improved sensitivity. Further tests of this 
second system are recommended. 

To assess the health impact of aldehydes as environmental 
pollutants, it is desirable to expedite measurements so that a maxima 
number of samples may be analyzed. With this in mind, we note that 
passive monitors offer a great potential for expediting large-scale 
sampling. Therefore, it is recommended that research be directed 
toward perfecting a passive-monitor trapping agent consistent with on 



16 

r more of the methods of analysis currently available. The 
ollection of aldehydes on solid sorbents and later removal with an 
ppropriate solvent represents one avenue of research. If they are 
onsistent with available methods of analysis, passive monitors could 
e deployed with minimal delay. 

There is no wet-chemical spectrophotometric method of analysis now 
vailable for the specific determination of acetaldehyde . Because the 
oxicity of acetaldenyde is low, relative to that of other aldehydes, 
his analysis may seem unnecessary and unimportant. However, 
icetaldehyde is a major source of peroxyacetyl nitrate in the urban 
nvironment, so it is very important to develop methods that allow the 
lonitoring of this major precursor of a highly toxic compound. It is 
'vident that the development of techniques for the quantitative 
inalysis of all the individual aldehydes present will permit the 
leasurement of acetaldehyde. 



HEALTH EFFECTS OF FORMALDEHYDE 

There is an urgent need for research to resolve several important 
questions related to the health effects of formaldehyde. The most 
loteworthy needs that the Committee has identified are outlined here. 

It is not known what fractions of persons with asthma, atopic 
subjects, nonatopic persons, and patients with chronic obstructive 
Lung disease constitute susceptible populations. Quantitative 
information on the proportion of the general population that is 
susceptible to the effects of formaldehyde and on the extent of the 
variability in response among this population may be obtained with 
appropriate epidemiologic techniques. A practical means for 
identifying susceptible subjects in the population is needed. Whether 
children, infants, pregnant women, older persons, and persons with 
specific medical conditions (e.g., heart disease) are also susceptible 
to the effects of formaldehyde also needs to be explored. 

Controlled studies of the range of irritation responses to 
formaldehyde at concentrations below 1 ppm are few. Both 
epidemiologic studies and human inhalation experiments are necessary 
to assess the risk more precisely. These studies should include 
several formaldehyde concentrations below 1 ppm. 

More objective means for determining human eye, nose, and throat 
irritation responses are needed. The reported studies have relied on 
subjective complaints. Because small-airway involvement may be a 
manifestation of lung involvement, future studies should incorporate 
tests of small-airway function, as part of both epidemiologic and 
chemical inhalation studies with humans. 

In general, to identify specific health effects associated with 
exposure, information is needed from extensive, long-term 



17 

epidemiologic studies that include persons from selected occupational 
sites and residences (conventional homes and mobile homes) and that 
involve cohorts (especially pregnant women, neonates, older children, 
and the infirm) and proper controls. Investigations should explore 
ways of identifying exposure with biologic tests (e.g., on urine or 
blood) and comparing them with the concentrations of chemical 
contaminants in air. Data on dose-response relationships are needed 
for use in developing control strategies. In addition, there must be 
careful documentation to show the relationship of human exposure to 
complaints, particularly nonspecific symptoms (headaches, tiredness, 
thirst, drowsiness, etc.). 

Human epidemiologic investigations assessing the carcinogenic 
potential of formaldehyde are lacking. Human studies should address 
carefully the magnitude and duration of exposure, cigarette-smoking 
habits, and the presence of other environmental contaminants, such as 
bis (chloromethyl) ether , or confounding factors. Animal studies should 
include a number of different species, including primates. The 
importance of hyperplasia and metaplasia of nasal mucosa in humans and 
animals requires clarification, including the natural history and 
sequence of changes, dose-response relationships, the regression of 
lesions after removal of formaldehyde exposure, and potential 
screening tests of value (such as nasal swabs for cytologic 
examination) . 

Long-term effects of continuous low-dose exposure to formaldehyde 
are not known; particularly needed is an assessment of the mutagenic, 
embryotoxic, and teratogenic potential through human epidemiologic and 
laboratory animal studies. The observation of the mutagenic potential 
of formaldehyde in a wide variety of organisms points to the need for 
new work to ascertain the mutagenic and carcinogenic potential of 
formaldehyde in mammalian germinal or somatic cells. This information 
is required to evaluate properly the hazard to persons exposed to 
formaldehyde. 

The mechanism of the airway response to formaldehyde is not 
known. Controlled inhalation studies with histamine or methacholine 
challenge tests are needed for assessing formaldehyde's effects on 
airways. Tests can be performed before and after low-dose exposures. 
In addition, investigations should be made to identify how 
formaldehyde sensitizes the airways and to determine whether there is 
an immunologic or nonimmunologic basis. 

Epidemiologic studies of dermatitis due to formaldehyde are needed 
in determining prevalence, clinical history, and other contributing 
factors. Epidemiologic studies evaluating the risk and nature of skin 
reactions should include formaldehyde patch tests. It is not known 
whether airborne formaldehyde can cause allergic skin reactions. 
Therefore, studies of this and other routes of exposure and of the 
skin metabolism of formaldehyde are needed. 

The effects of formaldehyde on nasal and lung defense mechanisms 
have not been well studied. More investigations showing the 
relationship of formaldehyde exposure and resulting effects on nasal 
and bronchial ciliary motility, alveolar machrophage function, and 
other defense processes are needed. 



18 

Limited information is available on the interactions of 
formaldehyde with other air pollutants. These studies are best 
performed as inhalation experiments, in which important variables can 
be controlled better than in field studies. The persons studied 
should include those believed to be susceptible to the effects of 
formaldehyde. 



HEALTH EFFECTS OF SOME OTHER ALDEHYDES 

Some of the higher-molecular-weight aldehydes appear to have 
effects that demand confirmation and quantitative evaluation to 
provide the proper health-risk evaluation and development of control 
strategies. Acetaldehyde was reported to be both embryotoxic and 
teratogenic in a single study in mice. These effects were similar to 
those of ethanol in humans. Because of the metabolic relationship 
between ethanol and acetaldehyde, the effects on the embryo need to be 
examined more extensively in other animal models. Acetaldehyde was 
shown to have chromosome-breaking activity in mammalian cells; that 
indicates that it may have mutagenic potential. Epidemiologic 
evidence also indicates that alcoholics have a higher risk of cancer. 
Again, the close metabolic relationship of acetaldehyde and ethanol 
requires that the carcinogenic potential be assessed. None of the 
existing studies provides sufficient information for an analysis of 
risks to humans. 

Acrolein is seemingly one of the most acutely toxic and highly 
irritating of the aldehydes commonly encountered in the environment. 
In a single study in rats, acrolein was not found to be embryotoxic. 
However, the fetuses were not examined for malformations. Therefore, 
no information on the teratogenic potential of acrolein is available, 
and this should be studied further. Acrolein was not shown to be 
carcinogenic in a study on hamsters; there was a minimal effect on the 
carcinogenicity of benzo[a]pyrene. Both the cocarcinogenic effect and 
the carcinogenic potential of acrolein need to be evaluated further in 
other animal models, to determine whether the hamster is refractory in 
acrolein exposure studies. The intense eye irritation that is induced 
in humans by acrolein at very low concentrations should be 
investigated to establish the mechanisms that cause the severity of 
the reactions. 

Investigations are also needed to characterize further the effects 
of the common aldehydes (e.g., butyraldehyde and acrolein) on humans, 
especially at concentrations present in the workplace, home, and 
general environment. Studies are needed to assess the importance of 
low-dose chronic exposures and interactions with other atmospheric 
contaminants . 

Further studies are required to establish the suggested role of 
formaldehyde, acrolein, and possibly other aldehydes in eye irritation 
associated with high concentrations of photochemical smog. Tests for 
possible relations of eye irritation and formic acid, peroxyacetyl 
nitrate, and other products derived from the aldehydes should be made. 



19 

Human exposure to atmospheric aldehydes may be repetitive , as in 
occupational situations, or continuous, as in a residential 
environment contaminated with aldehydes from cigarette smoke, 
automobile exhaust, or out-gassing from aldehyde-containing consumer 
products. Animal studies are needed to investigate the 
pathophysiologic effects, immunologic aspects, and element's of 
sensitivity associated with continuous chronic exposure to aldehydes, 
for use in assessing the potential hazards and the results of 
epidemiologic studies. 



EFFECTS OF ALDEHYDES ON VEGETATION 

Several overt and subtle effects of aldehyde phytotoxicity have 
been reported in the very few studies of aldehydes that have been 
conducted. To understand the phenomenon fully, systematic studies 
like those conducted with the major air pollutants sulfur dioxide, 
ozone, and hydrogen-fluoride are recommended. The more common 
aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and 
acrolein should be used to screen economically important crops for 
sensitivity. Plant factors such as genetic variability, age, and 
nutrition and climatic and edaphic factors that influence plant growth 
should be examined to determine whether they increase plant 
susceptibility. Dose-response data should be obtained for the major 
aldehydes singly and in combination with each other and with other 
pollutants. In addition to visible injury (obvious symptoms), 
biochemical and physiologic alterations in plants should be assessed. 
The discovery of an aldehyde-sensitive "indicator" plant would prove 
useful in detecting aldehyde pollution in the environment. 



EFFECTS OF ALDEHYDES ON AQUATIC ORGANISMS 

Available data on the toxicity of aldehydes to aquatic organisms 
show that the acute toxicity of aldehydes can vary considerably. No 
toxicity data are available on the majority of the aldehydes that have 
been identified in aquatic systems. Although chronic effects are 
unlikely because of the instability of aldehydes in water, it is 
recommended that a program be developed and implemented to assess 
systematically the probable hazard of the commonly encountered 
aldehydes to aquatic life and to identify those which should be 
controlled. 



CHAPTER 4 
COMMERCIAL PRODUCTION, PROPERTIES, AND USES OF THE ALDEHYDES 



The aldehydes are a very important class of organic compounds; 
they are characterized by the presence of the formyl functional group, 







which we represent in this report as -CHO. The general structural 
formula of the aldehydes can be written as 



R-C-H 

The first member of the aldehyde family is formaldehyde (HCHO) , in 
which the R group is a hydrogen atom. For the higher aldehydes, 
acetaldehyde (CH 3 CHO) , propionaldehyde (C 2 H 5 CHO) , and 
n_-butyraldehyde (n-C 3 H 7 CHO) , the R groups are CH 3 , C 2 H 5 , and 
n-C 3 H 7 , respectively. The physical properties of the aldehydes 
that have some potential importance in the environment are summarized 
in Table A-l of the Appendix. Table A-2 summarizes the uses of 
selected aldehydes and presents the various synonyms for their names. 

Formaldehyde is the most common and important aldehyde in the 
environment, and the properties of its several common forms are 
considered in some detail in the first section of this chapter. In 
subsequent sections we consider the methods of aldehyde production and 
the manufacture of aldehyde-containing consumer products. 



PROPERTIES OF VARIOUS FORMS OF FORMALDEHYDE 
MONOMERIC FORMALDEHYDE 

Monomer ic formaldehyde is a colorless gas that condenses to form a 
liquid of high vapor pressure that boils at -19C (760 Torr) ; it forms 
a crystalline solid at -118C. It has a pungent odor that is highly 
irritating to the exposed membranes of the eyes, nose, and upper 

20 



21 

respiratory tract. In the pure dry, liquid form at low temperatures 
(-80 to -117C) , it does not polymerize rapidly; its stability depends 
on its purity, and it must be held at a low temperature to avoid 
polymerization. It is not commercially available in this form, but 
can be prepared for laboratory use by the original method of Spence 
and Wild. 23 

The molecule of gaseous formaldehyde in ambient air is designated 
by the molecular formula HCHO or the structural formula, 

H 

> = 
H 

TRIOXANE 

Trioxane is the cyclic trimer of formaldehyde (trioxymethylene) . 
It has the molecular formula of 03^03, with three HCHO units 
per molecule. Its structural formula is: 

CH 2 

CK M) 

I I 

CH 2 CH 2 



In pure form, it is a colorless, crystalline solid that melts at 
61-62C, and it boils at 115C. It has a chloroform-like odor, and it 
is not irritating. It is combustible and burns readily when ignited 
(flash point, 45C) . It is soluble in water, and saturated solutions 
contain approximately 21 g/100 cc at 25C. 



PARAFORMALDEHYDE 

Paraformaldehyde is a colorless solid in a granular form with an 
odor characteristic of monomer ic formaldehyde. It is prepared by 
condensation of methylene glycol (HOCH 2 OH) , and its composition is 
best expressed by the formula HO- (HCHO) Q -H. Commercial grades of 
Paraformaldehyde usually specify not less than 95% formaldehyde by 
weight, and they may contain up to 99%. Paraformaldehyde melts over a 
wide temperature range (120-170C) , which depends on the degree of 
polymerization. At room temperatures, it gradually vaporizes largely 
as the monomer ic formaldehyde with some water formation, and the rate 
is increased by heating. Thus, it is commonly used as a source of 
formaldehyde for disinfecting large areas. It dissolves in hot water, 
and a solution of approximately 28% can be obtained by agitating it 
with water at 18C for 5 wk. 



22 

FORMALIN 

Formalin is the principal form in which formaldehyde is marketed; 
it is an aqueous solution that ranges in concentration from 37 to 50% 
by weight. The National Formulary solution contains not less than 37% 
formaldehyde with methanol (usually 6-15%, depending on the usage 
requirements) to suppress polymerization. It is a clear solution with 
the strong pungent odor of formaldehyde. Cloudiness is usually due to 
polymers, which form at various rates that depend on methanol content 
and storage temperature. The solution is slightly acid 0.005-0.01 M, 
calculated as formic acid. 

In aqueous solutions, the dominant form of the formaldehyde is 
methylene glycol; in concentrated solution, it is one of many polymer 
molecules, HO- (CH 2 0) n -H, polyoxymethylene glycol. 

SOME CHEMICAL REACTIONS OF FORMALDEHYDE 

Formaldehyde vapor is relatively stable with respect to thermal 
decomposition; at temperatures above 400C, it decomposes to form 
carbon monoxide, hydrogen, and methanol in the overall reactions, 

2HCHO + CH 3 OH + CO (1) 

and HCHO - CO + H 2 (2) 

Reaction 1 is catalyzed on metal surfaces and must occur 
heterogeneously. * l "* Reaction 2 may occur as written i.e., a 
direct decomposition into two stable molecules or it may occur by a 
free radical pathway initiated by a primary rupture of a 
carbon-hydrogen bond: HCHO + H + HCO; H + HCHO H 2 + HCO; HCO 
+ M t- H + CO + M. 

The carbon-hydrogen bonds in the formaldehyde molecule are 
relatively weak, and the rate constants for the hydrogen-atom 
abstraction reactions by free radicals are large (see Chapter 5) . For 
example, the HO-radical attack on formaldehyde, HO + HCHO + H 2 + 
HCO, has a rate constant that is near the collision number and is 
independent of the temperature. 

Formaldehyde monomer vapors at pressures above about 0.5 Torr show 
a tendency to polymerize at room temperature. 22 The equilibrium 
vapor pressure of monomeric HCHO over polymeric HCHO is much higher at 
high temperatures, and monomer pressures of several hundred Torr can 
be maintained readily for several hours without substantial 
polymerization if the containing vessel is heated to 100C or higher. 

In the aqueous phase, formaldehyde is oxidized readily by even 
mild oxidizing agents, such as Ag(NH3) 2 + , and this property has 
been exploited in the development of several wet-chemical analytical 
methods for formaldehyde. 



23 

OXIDATION AND REDUCTION REACTIONS 

On oxidation under controlled conditions in the gaseous or 
dissolved state, formaldehyde may be converted in part to formic acid, 
or under more highly oxidative conditions to carbon monoxide (with 
some carbon dioxide), and water. The photooxidation of formaldehyde 
in the gas phase leads to carbon monoxide, hydrogen, hydrogen 
peroxide, formic acid, and some other metas table products (see Chapter 
5) . Per formic acid is produced under special conditions through the 
oxidation of formaldehyde solutions at low temperatures. 

REACTIONS OF FORMALDEHYDE WITH FORMALDEHYDE 
Cannizzaro Reaction 

This reaction involves the reduction of one formaldehyde molecule 
with the oxidation of another. Although it is normally catalyzed by 
alkalies, the reaction can occur when formaldehyde is heated with 
acids at 40-60C: 2HCHO(aq) + H 2 * CH 3 OH + HCO 2 H. At 70C, 
the reaction may proceed through an aldol condensation, wherein 
carbohydrates are formed. Formaldehyde and other aldehydes that do 
not possess alpha-hydrogen atoms do not undergo ordinary aldol 
condensations, but can react almost quantitatively in alkaline 
solution and liberate hydrogen: 

HCHO(aq) + NaOH * HC0 2 Na + H 2 
H 2 + HCHO(aq) + CH 3 OH 

Tischenko Reaction 

Polymers of formaldehyde when heated with either aluminum or 
magnesium metal powder form methyl formate: 

2 HCHO( polymer) * HC0 2 CH 3 

Polymerization Reactions 

The formation of resinous products on reaction with other 
chemicals is one of the most useful characteristics of formaldehyde 
and is the reason for its immense importance in the synthetic resin 
industry. Under suitable conditions, the molecules of many compounds 
are linked together by methylene groups when subjected to the action 
of formaldehyde. Phenol- and urea-formaldehyde resins are 
polymethylene compounds of this type. 

Two distinct mechanisms are probably involved in resin-forming 
reactions: the polycondensation of simple methyl derivatives and the 
polymerization of doubled-bonded methylene compounds. Although in 
some cases the mechanism is definitely one or the other of the two, it 



24 

is often not clear which is followed, and both may play a part in some 
instances. Recent evidence indicates that the formation of 
urea- formaldehyde resins, which used to be regarded as a simple 
polycondensation of methylol ureas, may actually involve the primary 
formation of a methylene urea that then polymerizes to give a cyclic 
trimethylenetriamine whose methylol derivatives are finally 
cross-linked by condensation. 

Thermoplastic resins are the result of simple linear 

condensations, whereas the production of thermosetting resins involves 
the formation of methylene cross-linkage between linear chains. Both 
types may be produced from the same raw materials by variations in the 
relative amounts of formaldehyde used, the conditions of catalysts, 
and the temperature. However, with compounds whose molecules present 
only two reactive hydrogen atoms, only thermoplastic resins can be 
obtained. 

A diverse group of organic compounds including alcohols, amines, 
amides, proteins, phenols, and hydrocarbons form resins with 
formaldehyde. 



INDUSTRIAL PRODUCTION AND USES OF THE ALDEHYDES 

Aldehydes as a family are produced in the United States at a rate 
of several billion pounds per year. 25 An even greater quantity is 
produced in other parts of the world. The more important aldehydes 
(on the basis of production rates) are made with feedstocks obtained 
from petroleum or natural gas; hence, they are generally considered to 
be petrochemicals. 

Several aldehydes find large and generally major uses as 
feedstocks for the production of other chemicals. Considerable 
amounts of several aldehydes are used captively in a given 
plant i.e., they are produced and used in the same plant. Large 
quantities of aldehydes, however, are transported to other plants or 
locations for use. The following factors are considered here with 
respect to the most important aldehydes: industrial processes used 
for production, annual rates of production, end uses, and properties. 



FORMALDEHYDE 
Production 

Formaldehyde is the most important aldehyde in the United States 
and in the remainder of the world, on the basis of rates of 
production. 25 Most formaldehyde is stored and transported as 
aqueous solutions containing 37-50% formaldehyde and 1-15% methanol. 
In 1978, total production capacity in the United States was about 9 x 
10 Ib of aqueous solution, or about 3.3 x 10 Ib on an anhydrous 
basis. Actual production is estimated to be only 70% of capacity, or 
approximately 6.3 x 10 9 Ib of formaldehyde solutions per year. It 



25 

is estimated that 65% of the formaldehyde produced is used in the same 
plant in which it is produced. 

Costs for transporting formaldehyde tend to be high, because water 
and methanol also need to be transported. Hence, as a general rule, 
formaldehyde solutions are transported only relatively short 
distances, and little formaldehyde is exported or imported. Several 
large formaldehyde plants are near lumber plants in the South and the 
far West, inasmuch as the two largest uses for formaldehyde solutions 
are in production of plywood and particleboard. 

Methanol is the starting feedstock for commercial production of 
formaldehyde. 5 7 10 15 21 27 For some 40 or 50 yr, methanol has 
been produced almost exclusively by the reaction of carbon monoxide 
and hydrogen under high pressure in the presence of catalysts. Both 
carbon monoxide and hydrogen are generally obtained from natural gas 
or petroleum fractions. Other materials that, at least in theory, can 
be used are coal, shale oil, oil from tar sands, and cellulose. Coal 
has already found limited use, and it will probably increase in the 
future. For at least the next 10 or 15 yr, however, petroleum-based 
hydrocarbons will probably remain the preferred feedstock for 
production of methanol. 

Methanol (wood alcohol) was produced in the early part of this 
century primarily from wood. But this process cannot compete 
economically with the process that uses petroleum-based feedstocks. 
Another process that is no longer economically feasible is a process 
in which propane and butane are partially oxidized to produce a wide 
variety of oxygenated products, including methanol, formaldehyde, and 
acetaldehyde. 2 

In the United States, 16 companies produce formaldehyde; 
capacities of formaldehyde plants vary widely from about 14 to 600 x 
10" lb/yr. 15 Three companies (Celanese, Borden, and Du pont) have 
over 50% of our national capacity. Two quite different processes are 
used. 5 7 10 19 20 In one, a mixture of methanol and oxygen is 
passed over a silver catalyst. The main reaction is the 
dehydrogenation of methanol: 

Ag 



Part of the hydrogen is oxidized with oxygen to produce water vapor. 

In the other process, a mixture of methanol and air is passed over 
a catalyst consisting of molybdenum and iron oxides. The main 
reaction is this oxidative dehydrogenation of methanol: 

Mo,Fe 
CH 3 OH + 2 OXlde ^ HCHO + H 2 

Relative advantages of the two processes have been discussed in 
considerable detail by Diem, 7 Sleeman, 21 and Chauvel et al. 5 
The capital costs of the silver-catalyst process are higher, but its 
operating costs are lower. The ratio of formaldehyde to methanol in 



26 

the product solution is normally higher in the oxide-catalyst process; 
this product is preferred for some end uses. 5 



Uses 

Major uses for formaldehyde have been reported elsewhere. 9 2 * 
About 50% of the formaldehyde produced is consumed in the production 
of urea-formaldehyde and phenol-formaldehyde resins. These resins are 
used in the production of plywood, particleboard, foam insulation, and 
a wide variety of molded or extruded plastic items. Another 20-25% is 
used in the production of other resins or high polymers, including 
polyacetals, melamine resins, and alkyd resins. Hence, 70-75% of the 
formaldehyde is used in the production of high-polymeric resins or 
plastics. Formaldehyde is also used to produce 
hexamethylenetetramine, pyridine, trioxane, paraformaldehyde, 
chelating agents, and nitroparaffin derivatives. Formaldehyde 
solutions (often referred to as formalin) are used as disinfectants, 
embalming fluids, and textile-treatment agents and in leather and dye 
manufacture. 



ACETALDEHYDE (CH-jCHO) 



Production 

In 1978, production capacity for acetaldehyde in the United States 
totaled about 1.7 x IQr Ib, but actual production was approximately 
1.0 x 10 9 Ib. 17 2 " Acetaldehyde is generally stored and 
transported as a liquid. Because it has a normal boiling point of 
20.8C, storage vessels must be capable of withstanding high pressures, 

About 80% of the world's aldehyde is produced by controlled 
oxidation of ethylene with an aqueous solution of palladium and cupric 
chlorides as catalysts. x The overall desired reaction is as follows: 

C 2 H 4 + 0.502 + CH 3 CHO 

This acetaldehyde process was first commercialized in about 
1960; 12 two versions are now used industrially. A two-stage version 
was developed by Wacker Chemie, but Farbwerke Hoechst has developed a 
one-step version. These two versions are often referred to as the 
Wacker process and the Wacker-Hoechst processes, respectively. 11 In 
both, more than 93% of the ethylene feedstock is converted to and 
recovered as acetaldehyde. Carbon dioxide, water vapor, and 
chlorinated hydrocarbons are byproducts. 

In the one-step process, oxygen is used as the oxidant. It is 
mixed with ethylene, and the mixture is bubbled upward through the 
catalytic solution. About 25% of the ethylene reacts per pass over 
the catalyst, and most of the unreacted ethylene is recovered and 
recycled to the reactor . 



27 

In the two-step process, ethylene is bubbled upward through the 
catalytic solution. The following reactions are the predominant ones 
in the first step of the process: 

C 2 H 4 + PdCl 2 + H 2 * CH 3 CHO + Pd + 2HC1 
and Pd + 2CuCl 2 PdCl 2 + 2CuCl 

In the second step, the catalyst solution is regenerated with air in a 
separate reactor, as follows: 

2CuCl + 2HC1 + 0.50 2 * 2CuCl 2 + H 2 

Almost all the ethylene reacts in a single pass through the reactor in 
the two-step version; hence, recovery and recycling of ethylene are 
not critical as a rule. 

In both versions of the process, acetaldehyde is separated from 
the exit gas stream from the reactor by water absorption, and an 
aqueous solution of acetaldehyde is produced. Unreacted ethylene, if 
any, is recycled to the reactor. There is always a need for a vent 
stream, to remove chlorinated byproducts. This vent stream contains 
some ethylene and low amounts of acetaldehyde; the exact 
concentrations of these materials in the vent stream apparently have 
never been reported for any specific industrial plant. If necessary, 
however, an absorber could be designed and operated to remove 
essentially all acetaldehyde from the vent stream. To prevent most of 
the combustible hydrocarbons, including acetaldehyde, from escaping to 
the surroundings, it is generally more economical to send the vent 
stream to a flare or to the furnace. In the one-step process, the 
vent stream has a substantial fuel value. 

Before development of the Wacker technology, the following two 
processes were of major importance: 

Hydration of acetylene. This process was commercialized in 
Germany during World War I. Several modifications have been reported, 
but the process has not been competitive with the Wacker-Hoechst 
process, because of the relatively high price of acetylene, compared 
with ethylene. 

Dehydrogenation of ethanol. In many respects, this process 
is similar to the one for production of formaldehyde from methanol. 
To make its use feasible in the future, the required ethanol reactant 
must be available at a much lower cost than ethylene. 

Although these two process are still used to a limited extent, it 
is unlikely that they will be used in any new plants in the near 
future. 

In transporting or storing acetaldehyde, extensive precautions 
must be taken to prevent leaks and ensure safe conditions, because 
this aldehyde boils at room temperature. When mixed with air, it is 
highly flammable and reacts to form acetic acid, highly explosive 
peroxides, and other products. It is transported in drums or 
insulated trucks or tank cars. Specific information was not found on 
acetaldehyde concentrations in the atmosphere in or near acetaldehyde 
plants. 



28 

Uses 

About 60% of the acetaldehyde produced is used as feedstock for 
the production of acetic acid and acetic anhydride. The remaining 40% 
is used in the production of pentaerythritol, peracetic acid, 
pyridine, crotonaldehyde, 1,3-butylene glycol, and various other 
chemicals. Hester and Himmler 12 reviewed the numerous chemicals 
manufactured in 1958 from acetaldehyde. 

ACROLEIN (CH 2 =CHCHO) 

Production 

Acrolein is produced in the United States by Shell Chemical Co. 
and Union Carbide Corp.; the annual production in 1978 was estimated 
at about 45 x 10 6 Ib. 25 

Acrolein has been produced by several processes in the past, 
including condensation of formaldehyde with acetaldehyde and the 
pyrolysis of diallyl ether. 26 The method currently used is the 
catalytic oxidation of propylene; a mixture of propylene, air, and 
steam in a mole ratio of approximately 1:10:2 is passed over a 
catalyst of mixed metal oxides. Acrolein yields, on the basis of 
inlet propylene feed, are about 70%, but substantial amounts of 
acetaldehyde and acrylic acid are also produced. A water absorption 
unit and distillation are used for recovery and separation of 
acrolein, acetaldehyde, and acrylic acid. 

Acrolein is a colorless liquid; it is highly volatile and highly 
reactive. Because it is highly irritating, absorbers are used to 
minimize acrolein losses to the atmosphere. In addition, gaseous 
emission streams are generally sent to either a flare or a furnace, to 
destroy acrolein in any gas stream by combustion before it is 
exhausted to the atmosphere. Careful design and close attention to 
operating and maintenance procedures are necessary to minimize 
acrolein losses or leaks at pumps, valves, and storage vessels. 
Undesired reactions of acrolein, such as polymerization, are minimized 
by adding inhibitors and stabilizers to the liquid acrolein. 



Uses 

Approximately half the acrolein produced is used as a feedstock 
for production of glycerine, 26 and about 25% to produce the amino 
acid methionine, an essential protein added to various foods. The 
remaining 25% of acrolein is used in the production of many chemicals , 
including glutaraldehyde, 1,2,6-hexanetriol, quinoline, penta- 
erythritol, cycloaliphatic epoxy resins, oil-well derivatives, and 
water-treatment chemicals. 



29 

HIGHER ALIPHATIC ALDEHYDES 
Production 

The Oxo process is the application of a chemical reaction called 
oxonation, or more properly hydroformylation, for production of 
03-0^5 aliphatic aldehydes. 13 Carbon monoxide and hydrogen are 
caused to react with the double bond of an olefin to produce an 
aldehyde with at least one more carbon atom than the olefin. In the 
case of ethylene, the overall reaction for production of 
propionaldehyde is as follows : 

CH 2 =CH 2 + CO + H 2 - CH 3 CH 2 CHO 

In the case of proplyene, both n-butyr aldehyde and isobutyraldehyde 
are produced. 

In the past, cobalt carbonyls were used almost exclusively as 
catalysts for the Oxo process, and relatively high pressures, often 
200-400 atm, were required. 13 In the last few years, various 
catalysts have been proposed that offer a variety of advantages, 
including higher yields, improved product compositions, and lower 
operating pressures. Rhodium catalysts, for example, are now widely 
used in Oxo processes of at least several olefins. 16 

A portion of the aldehyde formed is hydrogenated to produce 
alcohols. For example, some propionaldehyde is hydrogenated to 
1-propanol, some iv-butyraldehyde to 1-butanol, and some 
isobutyraldehyde to 2-butanol. 

Propionaldehyde is produced by two American manufacturers, Eastman 
Kodak Co. and Union Carbide Corp. Production in 1978 was estimated at 
over 190 x 10 6 lb. 25 About 750 x 10 6 Ib of butyraldehydes were 
produced in 1976. Major American' producers of butyraldehyde are 
Badische, Celanese Corp., Eastman Kodak Co., and Union Carbide Corp. 

The Oxo process is used for the manufacture of several aldehydes 
that are consumed in the production of plasticizers. In such cases, 
the aldehydes are hydrogenated to produce alcohols; the alcohols then 
react with acids to produce the esters that serve as plasticizers. 



Uses 

Propionaldehyde is used primarily as a chemical intermediate; the 
percentages consumed in this country for different purposes are 
approximately as follows: 1-propanol, 40%; propionic acid, 37%; and 
trimethylolethane, 23%. Butyraldehydes are used as chemical 
intermediates in the production of 1-butanol, 2-butanol, 
2-ethyl-l-hexanol , and a wide variety of specialty chemicals. Over 
1 x 10 9 lb of plasticizers are used each year in the preparation of 
poly (vinyl chloride) plastics; C4~Ci2 aldehydes are used for this 
purpose. Several of the higher aliphatic aldehydes, 



30 

particularly C^~ C 16 aldehydes, are used in the production of 
detergents. 



BENZALDEHYDE (C 6 H 5 CHO) 

Benzaldehyde is a colorless or yellowish, highly refractive oil 
with an odor resembling that of oil of bitter almonds; it is the 
simplest aromatic aldehyde. 6 Total world production is probably 
less than 10 x 10 6 Ib/yr . 

Toluene is the feedstock used for production of benzaldehyde. At 
least three processes have been used industrially: 6 

Toluene is chlorinated to produce benzal chloride (or 
a, ordichlorotoluene) , which is then hydrolyzed to produce 

benzaldehyde. 

Liquid toluene is oxidized in the presence of a catalyst, 

such as manganese dioxide. 

Toluene vapors are oxidized on a catalyst, such as vanadium 
pentoxide. 

Major U.S. producers of benzaldehyde are Benzol Products Co., 
Heyden, Newport Chemical Corp., and Tennessee Product and Chemical 
Corp. 



Uses 

Benzaldehyde has important uses in dyes, Pharmaceuticals, 
perfumes, and flavoring agents. 

FURFURAL 

EC' ^C-CHO 

II II 
HC CH 

Production 

Furfural (2-furaldehyde, furfuraldehyde, furfurol, or furol) , a 
colorless liquid aldehyde is produced from a variety of agricultural 
byproducts, including corncobs, oat hulls, rice hulls, bagasse, 
cottonseed hulls, and paper-mill wastes. 8 It is soluble in most 
organic solvents, but only slightly soluble in water. Furfural is 
essentially a substituted furan; the aldehyde group is attached to the 
five-member heterocyclic ring that contains one oxygen atom and two 
carbon-carbon double bonds. 

The raw materials used for furfural production are typically 
brought together in dilute sulfuric acid, and the mixture is heated 



31 

pressure. On completion of the reaction the pressure is 

-ed, causing the furfural to vaporize, with considerable water. 

ude furfural is then purified primarily by distillation. 



irfural is used in the manufacture of furan and several 
lydrofuran compounds. It is used extensively as a selective 
it in the production of lubricating oils, gas oils, diesel fuels, 
jgetable oils. It also finds uses in the production of modified 
L-formaldehyde resins and in the extractive distillation of 
.ene. 



MANUFACTURE OF ALDEHYDE-CONTAINING CONSUMER PRODUCTS 
FORMALDEHYDE RESINS 

Dme urea-formaldehyde resins emit formaldehyde over extended 

3s. A brief discussion of the manufacturing (or polymerization) 

ique used to produce these resins will help to explain the 

ion problem and will suggest ways to eliminate or at least 

ize it. The resins are prepared by causing urea to react with 

Idehyde. 3 Each of the four hydrogen atoms in a urea molecule 

tentially reactive. If urea and formaldehyde reacted on an 

ly equimolar basis, the following reactions indicate the 

tion of a typical so-called thermoplastic resin (or high polymer) 

H-N-H H-N-CH 2 OH 

C = +HCHO -- C = 
I I 

H-N-H H-N-H 

urea 

'he intermediate product formed is basically a monomer, and it 
lerizes as follows to produce a thermoplastic resin and water: 



H-N-CH 2 OH H-N-CH 2 -N-CH 2 OH 

I I I 

C = *- C = O C = O + H 2 

H-N-H H-N-H H-N-H 



32 
Eventually: 

r~ -~ 

H-N-CH 2 OH H N-CH 2 OH 

n C = *- C = + (n-l)H 2 

H-N-H H-i-H 



Some additional formaldehyde is, however, needed to react with at 
least a few of the unreacted -NH 2 groups and to provide chemical 
cross-links between polymer chains. When such cross-links occur, the 
desired thermosetting polymers or resins are produced. The amount of 
formaldehyde added to the reaction mixture is critical, for the 
following reasons: 

An excess of formaldehyde results in faster polymerization or 
cross-linking, which tends to lower manufacturing costs. 

Sufficient formaldehyde is needed to provide adequate 
cross-linking and to cause satisfactory properties in the final 
product. 

An excess of formaldehyde results in unreacted formaldehyde 
in the final consumer product, which slowly diffuses from the product 
and, especially in indoor applications, may result in increased 
formaldehyde concentrations. 

In addition to unreacted formaldehyde in urea-formaldehyde resins, 
some formaldehyde may be formed by hydrolysis involving these resins. 
These hydrolysis reactions are essentially the reverse of the 
reactions shown above. When the resins are exposed to water or to a 
humid atmosphere, some moisture is adsorbed; this results in the slow 
formation and release of formaldehyde. Factors that affect the 
release of formaldehyde from UF resins are discussed in greater detail 
by Meyer . l 8 

Urea-formaldehyde resins are a large and relatively old family of 
high polymers that have been used in the production of numerous molded 
plastic items. With respect to the release of formaldehyde to the 
air, definite problems have occurred in the following applications: 

Foams used in walls or attics of homes or other buildings for 
insulation. 

Particleboard. 

Indoor plywood. 

Paper products and some textiles. 

In plywood and particleboard, the role of the resin is to act as 
an adhesive to bind the thin sheets of wood and wood particles 
together . 



33 

OTHER CONSUMER PRODUCTS 

Several other high polymers that are prepared with formaldehyde 
probably contain unreacted formaldehyde that may eventually be 
emitted, phenol-formaldehyde (or phenolic) resins are prepared by 
causing phenol and formaldehyde to react. Melamine resins are 
reaction products of melamine and formaldehyde. The amount of 
unreacted formaldehyde in the resin is obviously important. Phenolic 
and melamine resins can be used as adhesives in the production of 
plywood and particleboard . Phenolic resins are used because of their 
desirable physical and chemical properties: they are quite resistant 
to hydrolysis; they are relatively inexpensive , compared with 
alternative resins (but somewhat more costly than urea-formaldehyde 
resins) ; and there are often some problems with appearance. Although 
plywood produced with phenolic resins is often dark or somewhat 
stained, it is usually covered or coated in some way. Loss of 
formaldehyde in such plywood, it it does actually occur, would be less 
critical, because of outdoor application. There is little likelihood 
that aldehyde would ever build up to high concentrations in the 
ambient air. 

Both phenolic and melamine resins are used in large quantities to 
fabricate numerous molded or extruded plastic products. Because 
fabrication is at high pressure, the final plastic product has 
essentially no porosity. Hence, in these products, diffusion of 
unreacted formaldehyde to the surface is extremely slow. There is no 
evidence that formaldehyde emission is a problem with phenolic or 
melamine plastic products. 

Polyacetal resins are formed by polymerization of formaldehyde or 
trioxane. Ethylene oxide is sometimes used as a comonomer , and the 
polyacetal resin is a copolymer . At or near ambient conditions, 
polyacetals are highly stable. Polyacetals that are homopolymers of 
formaldehyde are thermally unstable at high temperatures, such as 
might be experienced during a fire. In such cases, they decompose 
quite rapidly and release formaldehyde. 



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34 

6. Darshau, P., and A. P. Kudchadker. Benzaldehyde, pp. 171-182. In 
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14. Longfield, J. E., and W. D. Walters. The radical-sensitized 
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15. Lovell, R. J. Emissions Control Options for the Synthetic Organic 
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16. Low-pressure Oxo process yields a better product mix. Chem. Eng. 
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17. Ma, J. J. L. Acetaldehyde. Process Economics Program Interim 
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18. Meyer, B. Urea-Formaldehyde Resins. Reading, Mass.: 
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formaldehyde solutions. Chem. Eng. 75:42-44, 1 January 1968. 



35 

22. Spence, R. The polymerisation of gaseous formaldehyde. J. Chem. 
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25. Suta, B. E. Production and Use of 13 Aldehyde Compounds. Menlo 
Park, Cal.: SRI International, for U.S. Environmental Protection 
Agency, Office of Research and Development, 1979. [32] pp. 

26. Weigert, W. M. , and H. Haschke. Acrolein and derivatives, pp. 
382-401. In J. J. McKetta and W. A. Cunningham, Eds. 
Encyclopedia of Chemical Processing and Design. Vol. 1. New 
York: Marcel Dekker, Inc., 1976. 

27. Weimann, M. More-methanol formaldehyde route boasts many 
benefits. Chem. Eng. 77:102-104, 9 March 1970. 



CHAPTER 5 

ALDEHYDE CONCENTRATIONS, EMISSION, AND ENVIRONMENTAL GENERATION 
AND TRANSFORMATION REACTIONS 



The aldehydes are introduced into the environment through a 
variety of different pathways, which are considered in this chapter. 
They are injected directly into the atmosphere with exhaust gases from 
mobile sources and other equipment in which the incomplete combustion 
of hydrocarbon fuels occurs. They arise from various industrial and 
manufacturing operations and power generating plants that burn fossil 
fuels, from uncontrolled forest fires and the open burning of wastes, 
and from vegetation. Aldehydes are also generated in the atmosphere 
through the interaction of various reactive species (ozone, hydroxyl 
radicals, etc.) with hydrocarbons and some of their oxidation 
products. In recent years, it has been recognized that formaldehyde 
vapors may be released indoors, as well as outside, from various 
domestic activities and, more importantly, from particleboard and 
other building and insulation materials, chemically treated cloth, and 
other products that are formulated with formaldehyde-containing 
polymers. In fact, indoor concentrations of the aldehydes generally 
exceed those found in the outside air today. 

The buildup of aldehydes in the atmosphere as the result of their 
direct release and their atmospheric generation is counterbalanced by 
many aldehyde removal paths. The aldehydes absorb the ultraviolet 
component of sunlight and undergo photodecomposition. They also react 
rapidly with the ubiquitous, highly reactive, transient hydroxyl (HO) 
free radical present in sunlight-irradiated atmospheres. Because of 
the high water solubility of formaldehyde and the other 
low-molecular-weight aldehydes, one expects the transfer of aldehydes 
into rainwater, the oceans, and other surface waters. 

The rates of generation of ozone and the peroxyacylnitrates in the 
polluted atmosphere are strongly influenced by aldehyde 
photodecomposition and other reactions. 

The combined effects of aldehyde injection, generation, and 
removal lead to a highly variable ambient concentration of the 
aldehydes. Their concentration can become high (about 0.05 ppm) in 
areas of high human activity and poor atmospheric ventilation. They 
are also present in the natural atmosphere, and concentrations of 
0.002-0.006 ppm are commonly monitored in remote regions. 
Concentrations many times higher have been reported in some 
nonoccupational indoor environments. This chapter considers the 

36 



37 

aldehyde concentrations observed and then f in more detail, the many 
processes that control these concentrations. Throughout this 
document, the concentrations of gaseous aldehydes are usually given in 
parts per million (ppm) or micrograms per cubic meter (yg/m 3 ) . 
"Parts per million" as used here refers to molecules of the species in 
question per million molecules of air at 25C and 1 atm; for these 
conditions, concentrations expressed in the two units may be 
interconverted according to the following relations: 

concentration in yg/m 3 = (concentration in ppm) (40.87) (M) , and 
concentration in ppm = (concentration in yg/m 3 ) (0.02447)/ (M) , 
where M is the molecular weight of the specific aldehyde, e.g., 30.03 
for formaldehyde and 44.05 for acetaldehyde . "Parts per hundred 
million" (pphm) , "parts per billion" (ppb) , and "parts per trillion" 
(ppt) , which are used occasionally, refer to molecules of the species 
in question per hundred million, billion, and trillion molecules of 
air (at 25C and 1 atm), respectively. 



ENVIRONMENTAL CONCENTRATIONS OF THE ALDEHYDES 
THE CLEAN ATMOSPHERE 

The formation of formaldehyde and the other aldehydes in the 
natural unpolluted atmosphere is both anticipated in theory and 
observed experimentally. Reported ranges of concentration of total 
aldehydes in ambient clean air are as follows: Antarctica (1968) , 
<30. 0005-0. 01 ppm; rural Illinois and Missouri (1973), 0.001-0.002 
ppm; Panama (1966), <0. 0002-0. 0027 ppm; and Amazon basin (1970), 
0.001-0.006 ppm 25 (Breeding et^ al^ , 2 5 in reporting concentrations 
in the central United States, cited references to other measurements 
of formaldehyde in clean air) . Spectroscopic measurements 
(high-resolution infrared absorption) have been used to identify 
formaldehyde in the atmospheric column over Reims, France. 15 From 
an analysis of the absorption line shapes at 2806.858 and 2869.871 
cm"-'- and reference to theoretical formaldehyde concentration- 
altitude profiles, Barbe et al. derived the approximate formaldehyde 
concentration-altitude profile shown in Figure 5-1 (dashed line). 15 
The formaldehyde concentration decreased from about 10 10 
molecules/cc (about 0.0004 ppm) at ground level to about 10' 
molecules/cc (about 0.00002 ppm) at 26 km. These measurements are in 
reasonable accord with the theoretical estimates of Levy, 113 which 
are shown in Figure 5-1 as the solid curve. 



URBAN ATMOSPHERES 

Aldehydes are among the most abundant of the carbon-containing 
pollutant molecules in most urban atmospheres; only the hydrocarbons, 
carbon monoxide, and carbon dioxide are at higher concentrations. 
Shown in Figures 5-2, 5-3, and 5-4 are the aldehyde concentrations 
observed in the areas of Los Angeles, California, in 1968, 15G 



38 



30 



r 



20- 



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FIGURE 5-2 Hourly aldehyde concentrations at Huntington Park and El Mon 
Calif., October 22 1968. Reprinted with permission from Scott Research 
Laboratories, Inc. 



40 



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I 

CJ 

I 

I 
o 
o 
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20 - 




1000 




1400 1600 

TIME (hours) 



1800 



2000 



FIGURE 5-3 Concentrations of formaldehyde and formic acid measured 
in Riverside, Calif., at various times on October 14, 1977. Reprinted 
with permission from Tuazon ^t aJL. 



41 



12 



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at Newark, N.J. , for different days of the week; averaged from data 
taken from June 1 to August 31 for 19^, 1973, and 1974. Reprinted 
with permission from Cleveland e_t al. 



42 

Riverside, California, in 1977, 178 179 and Newark, New Jersey, in 
1972-1974. " 6 The relatively high concentrations of the aldehydes 
observed in Los Angeles some years ago in 1968 are not observed 
today. More typical are those shown in Figures 5-3 and 5-4. The 
diurnal variations observed reflect the meteorologic influence of air 
transport and mixing, as well as the other chemical and physical 
processes that form and remove these compounds. Table 5-1 summarizes 
additional analytic data for total aldehydes, formaldehyde, and 
acrolein as determined by chemical methods and reported in studies 
made in several large metropolitan areas. The data from the first 
four studies shown were obtained in the Los Angeles area and are based 
on averages of hourly samples taken only during the daylight hours. 
Data from the other studies shown are from annual averages of samples 
taken once each 24 h during the year. From these data and the more 
extensive data from urban centers in 26 states and 

Washington, D.C., 168 it appears that the 24-h average concentration 
of total aldehydes is frequently above 0.1 ppm (12 yg/m ) in many 
urban areas, but with wide variations; hourly daytime averages may be 
near 0.05 ppm (60 yg/in 3 ) and infrequently above 0.1 ppm (120 
yg/m 3 ) . 

The chemical nature of the mixture of aldehydes present in outdoor 
air is expected to be a function of the local emission sources and the 
meteorologic factors (sunlight intensity and wavelength distribution, 
temperature, etc.) near the sampling site. However, formaldehyde 
usually makes up some 30-75% of the total aldehyde observed in ambient 
urban air. The complete molecular speciation and composition are not 
now available for the fraction of the ambient-air samples determined 
to be "total aldehydes" by chemical methods, but all the normal 
aliphatic aldehydes containing 1-12 carbon atoms, the 14-carbon 
aldehyde, and a few of the common branched-chain aldehydes have been 
identified in ambient air. 73 Nine difunctional aldehydic compounds 
(Cc-, Cg-, and Cy-dialdehydes, hydroxyaldehydes , and aldehydic 
acids) have been detected in aerosols. A study carried out in 
California in 1972 included analysis for acetaldehyde, as well as 
formaldehyde. 33 Daily averages of formaldehyde were around 0.035 
ppm; those for acetaldehyde, the only other aldehyde identified, were 
about 0.02 ppm. 

Although Graedel 73 reported that only one of the aromatic 
aldehydes had been detected in ambient air (4-methylbenzaldehyde, at 
50-280 ppt) , benzaldehyde and 2-methylbenzaldehyde , 
3-methylbenzaldehyde, and 4-raethylbenzaldehyde probably are also 
present in at least minute amounts. Such a conclusion is based on two 
types of information: first, the latter aromatic aldehydes have been 
detected in the emission of automobiles burning gasolines that contain 
aromatic hydrocarbons (as is discussed in more detail later); second, 
on the basis of photooxidation investigations with toluene and xylenes 
(common ingredients of gasoline), such aldehydes are formed. 57 If 
the aromatic-hydrocarbon content of gasoline increases, the amounts of 
aromatic aldehydes present in the atmosphere will probably also 
increase. 



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Acrolein, the simplest unsaturated aldehyde, is of special 
interest, because of its effectiveness in inducing eye irritation and 
its general high toxicity. It appears to constitute a small but 
important fraction of the aldehydes in the urban atmosphere. Table 
5-1 shows that the average acrolein concentration is 8-26% of the 
average formaldehyde concentration. Scientists in Tokyo have reported 
an average acrolein concentration of 7.2 ppb (0.0072 ppm) , which is 
within the range shown in Table 5-1. 98a 

In summary, the present data suggest that in a clean, unpolluted 
atmosphere aldehyde concentrations at ground level are commonly about 
0.0005-0.002 ppm. In polluted urban ambient air, the concentrations 
are much higher commonly an hourly average of 0.01-0.05 ppm during 
the daylight hours. Formaldehyde is the dominant aldehyde present, 
and it usually makes up 30-75% of the total aldehyde present. Limited 
analytic data show that acetaldehyde may be present at about 60% of 
the formaldehyde concentration, and the higher aliphatic aldehydes are 
present at lower concentrations, decreasing rapidly with increasing 
molecular weight. Acrolein may be present at about 10-25% of the 
formaldehyde concentration; the aromatic aldehydes appear to make up 
only a few percent of the total aldehyde. Other dialdehydes or 
difunctional aldehydes presumably contribute to the aerosol mass in 
which they have been observed. 

There is now no quantitative rationale that we can invoke to 
explain the large day-to-day or even year-to-year variations in 
aldehyde and hydrocarbon concentrations in the atmosphere. 
Experimental evidence from Houston, for example, obtained from 1973 
through 1975 are most interesting in this regard. In some cases, the 
aldehyde concentrations were found to vary by a factor of 5-10 within 
several days. In one extreme variation, a reading of 52 yg/m 
(0.042 ppm) occurred a week after and a week before readings of 6-7 
jjg/ra 3 (0.005-0.006 ppm). In 1973, aldehyde values in Houston 
averaged higher than those in 1975 and especially those in 1974. No 
explanation was given for such differences. Atmospheric conditions 
must be responsible at least in part for day-to-day and year-to-year 
differences. The following are some of the factors that appear to be 
important in this variability: 

Wind conditions, including velocity and direction, strongly 
affect the dispersion of emission. 

Rain, standing water, or moist surfaces can be important 
sinks for formaldehyde. 

The extent of cloud cover and the position of the sun affect 
the sunlight intensity, which alters the rate of photochemical 
reactions. 

Air temperature affects the rate of chemical processes. 

Time of year may be important relative to atmospheric 
aldehyde concentrations; this is in part a result of temperature 
inversions that entrap the emission in the atmosphere near ground 
level. July through September, in general, had the highest 
concentrations in New Jersey, 1 * 6 Cincinnati, 93 and Houston. 93 



45 

\ direct comparison can be made between the ambient aldehyde 
entrations in and near Houston and Cincinnati from 1973 through 
and between the concentrations in these two cities and St. Paul, 
esota, in 1974. 93 The mean aldehyde concentrations in 
innati and St. Paul were in general slightly higher than those in 
ton. These results and a detailed analysis of the Houston data 
est that the major refineries and chemical complexes of the 
ton area do not contribute directly to the aldehyde 
entrations. Bay town, in the Houston area, is the home of major 
ning and chemical plants; yet it had one of the lowest aldehyde 
.entrations in the entire Houston area. This may result in part 
i the time required for the conversion of hydrocarbons, perhaps the 
>r impurity derived from the Bay town industry, to aldehydes through 
jspheric reactions. 

In 1973, the aldehyde concentrations in the Deer Park area of 
ston were very high rather consistently aoove those in any 
ghboring areas. There are several major refineries and 
cochemical plants in this area. In 1974 and in 1975, aldehyde 
centrations in Deer Park were similar to those in the remainder of 
Houston area. The reason for the large reduction in 1974 and 1975 
unknown . 

Aldehyde concentrations at or near Houston's and Cincinnati's 
or airports were similar to those in neighboring areas, 
'sumably, airports and planes contribute only a small fraction of 
> direct emission of aldehyde in metropolitan areas. 

It is clear that transport of the air masses, the height of the 
:ing layer, and other meteorologic factors can be important in 
:ermining ambient aldehyde concentrations. 



3 WORKPLACE 

Workers in plants producing plywood or particleboard often use 
ea-f ormaldehyde , phenol-formaldehyde, or melamine-formaldehyde 
sins. Formaldehyde concentrations in several such plants have been 
ported 21 66 82 177 193 and may be as high as 10 ppm. The 
>rmaldehyde concentrations in the air in these plants obviously 
pend on the ventilating systems. Other key variables include the 
lount of free formaldehyde in the resin, the moisture content of the 
>od, the humidity of the air in the plant, and the processing 
jmperatures. With current emission control technology, formaldehyde 
mcentrations are or can be substantially lower. 

Workers in a variety of other occupations are also exposed to 
>rmaldehyde , as shown in Table 5-2. 



ONOCCUPATIONAL INDOOR AIR 

The infiltration of outdoor air is one source of aldehydes in the 
ndoor environment, but the primary sources are building materials, 
ombustion appliances, tobacco smoke, and a large variety of consumer 



46 



TABLE 5-2 
Formaldehyde Measurements in Occupational Environments 



Sampling Site 



161 



Textile plants 



22 
Garment factory 



Clothing store 



128 



Smog chamber 



155 



Laminating plants 

102 
Funeral homes 



64 



Concentration, ppm 
Range Mean 



0-2.7 
0.9-2.7 

0.9-3.3 
0.01-unk 
0.04-10.9 
0.09-5.26 



0.68 



0.25-1.39 



Method of Analysis 

Sodium bisulfite, 

iodometric titration 

Collection in sodium 
bisulfite solution 

MBTH bubblers 
Chromotropic acid 
Chromotropic acid 
Chromotropic acid 



47 

products. Aldehydes can build up in buildings with greater insulation 
and tighter thermal containment intended to reduce infiltration (air 
exchange) and energy consumption. 

Measurements of aldehydes in the indoor environment have typically 
focused on formaldehyde, whose indoor concentrations generally exceed 
those outdoors. Indoor monitoring data for U.S. homes are few, but 
limited monitoring data do exist for European homes, particularly in 
the Nordic countries. Table 5-3 summarizes the data that were 
recently described in detail by Suta. * 7 ** 

Several studies have concentrated on indoor formaldehyde emission 
from particleboard and plywood furnishings in houses. Measurements in 
Denmark, 9 Sweden (T. Lindvall and J. Sindell, personal 
communication), West Germany (Deimel; 51 * B. Seifert, personal 
communication; Weber-Tschopp et_ al_. 19 ), and the United States (P. A. 
Breysse, personal communication) have shown that indoor concentrations 
often exceed 0.1 ppm and in some cases even exceed the 8-hr 
time-weighted average of 3 ppm for workroom air. 182 18S In 23 
Danish houses, the average formaldehyde concentration was 620 
Vig/nP (about 0.5 ppm), and the range was 80-2,240 yg/nr (about 
0.07-1.9 ppm) . 9 

Over the last several years, complaints about indoor air quality 
have come from residents of mobile homes (constructed with 
formaldehyde-containing indoor plywood and particleboard) . Since 
1978, the U.S. Consumer Product Safety Commission (CPSC) has received 
hundreds of such complaints. Other federal agencies have also 
reported an increased number of complaints. In addition, dozens of 
lawsuits have been filed against UF-foam manufacturers and installers 
and mobile-home builders. It has been estimated that one of every 20 
Americans perhaps 11 million people live in mobile homes that 
contain substantial quantities of particleboard, plywood, or both and 
are therefore potentially at risk of being exposed to formaldehyde. 
Thousands more live in homes insulated with UF foam. In August 1979, 
the CPSC issued two consumer advisories on UF insulation, citing 
possible health problems associated with this type of insulation. 

As a result of occupants' complaints, formaldehyde was measured in 
more than 200 mobile homes in the United States; the concentrations 
reported ranged from 0.03 to 2.4 ppm (about 37-2,940 ug/m 3 ) 
(Breysse, personal communication) . A study of formaldehyde emission 
in new office trailers with air-exchange rates as low as 0.16 air 
change per hour (ach) found formaldehyde concentrations in the range 
of 0.15 to 0.20 ppm, 60 in contrast with outdoor concentrations of 
less than 0.01 ppm. 

Formaldehyde vapors are a concern in mobile homes, not only 
because the building materials used in their construction typically 
contain formaldehyde, but also because mobile homes are more tightly 
constructed than conventional homes and thus have less ventilation. 

Aldehydes (measured by the MBTH method) were monitored in a study 
of 19 homes across the United States. 135 Outdoor concentrations 
were consistently lower than indoor concentrations typically by a 
factor of 6 and quite often by an order of magnitude. Figure 5-5 is 
an illustration of the data collected in this study. The observed 



48 

TABLE 5-3 
Summary of Aldehyde Measurements in Nonoccupational Indoor Environments 



Sampling Site 



8 



Danish residences 

Netherlands residence 
built without form- 
aldehyde-releasing 
materials 

Residences in Denmark, 
Netherlands, and 
Federal Republic of 
Germany 

Two mobile homes in 
Pittsburgh, Pa. 135 

Sample residence in 
Pittsburgh, Pa. 135 



Mobile homes register- 
ing complaints in 



26 



state of Washington 

Mobile homes register- 
ing complaints in 
Minnesota 67 

Mobile homes register- 
ing complaints in 
Wisconsin 

Public buildings and 
energy-efficient 
homes (occupied and 
unoccupied) 



Concentration, ppm 



Range 

1.8 (peak) 

0.08 (peak) 

2.3 (peak) 
0.1-0.8 b 



0-1.77 

0-3.0 

0.02-4.2 

0-0.21 
0-0. 23 b 



Mean 



0.03 



0.4 



0.36 



0.5 (peak) b 0.15 



0.4 



0.88 



Method of Analysis 

Unspecified 

Unspecified 

Unspecified 



MBTH bubblers 



MBTH bubblers 



0.1-0.44 Chromotropic acid 

(single impinger) 



Chromotropic acid 
(30-min sample) 



Chromotropic acid 



Pararosaniline and 
Chromotropic acid 

MBTH bubblers 



a Formaldehyde, unless otherwise indicated. 
b Total aliphatic aldehydes. 



"M. Woodbury, personal communication. 



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49 



50 

outdoor aldehyde concentration remained below 25 yg/m 3 (0.02 ppm) 
at all times. The study determined that its field sample comprised 
two distinct classes of residences: those with high and those with 
low aldehyde concentrations (see Table 5-4). In all cases, however, 
indoor aldehyde concentrations exceeded outdoor. Although the source 
strengths were not determined in this study, the highest 
concentrations were observed in the mobile homes, and the plywood and 
particleboard generally appeared to be the primary source. 

In a more recent study, formaldehyde and total aliphatic aldehydes 
(formaldehyde plus other aliphatic aldehydes) were measured at several 
energy-efficient research houses at various locations in the United 
States. 111 * At low infiltration rates (<0.3 ach) , indoor 
formaldehyde concentrations often exceeded 0.1 ppm (123 yg/nr) , 
whereas outdoor concentrations typically remained at 0.016 ppm 
(20 yg/m 3 ) or less. Normal air-exchange rates are about 
0.75/ach. Figure 5-6 is a histogram showing the frequency of 
occurrence of formaldehyde and total aliphatic aldehyde concentrations 
measured at an energy-efficient house with an average of 0.2 ach. 
Data taken at an energy-efficient house in Mission Viejo, California, 
are shown in Table 5-5. As shown, when the house did not contain 
furniture, formaldehyde concentration was 80 yg/m 3 ; when furniture 
was added, formaldehyde almost tripled. A further increase was noted 
when the house was occupied, very likely because of such activities as 
cooking with gas. When occupants opened windows to increase 
ventilation, the formaldehyde concentration decreased substantially. 
Although high, aldehyde concentrations observed in most of the 
energy-efficient dwellings that have been monitored were generally 
below 200 ug/m 3 . 

Indoor and outdoor formaldehyde/aldehyde concentrations were found 
to be about the same at a public school in Columbus, Ohio, and a large 
medical center in Long Beach, California, and were well below 0.1 ppm 
(120 yg/m 3 ) . Both buildings have high ventilation rates, and that 
is probably why the indoor concentrations were low and essentially 
equivalent to outdoor concentrations. 

Because many of the data reported from these field-monitor ing 
studies involved houses whose occupants had complained of indoor air 
quality, these findings may not be representative of all homes. 
However, when data from the Washington sample, which was random, are 
compared with those from the mobile-home sample, which was based on 
occupant complaints, most of the differences in aldehyde concentration 
can be explained by differences in the age of the home. The mobile 
homes in the complaint sample are much newer than those in the random 
sample. Moreover, when Tabershaw ^t al. 1 ?s analyzed the complaint 
data on mobile homes in Washington, it was found that there was no 
valid relationship between the degree of symptoms reported by 
occupants and the concentrations of formaldehyde and that, regardless 
of the actual exposure, all persons in the mobile-home sample reacted 
in substantially the same manner. Tabershaw Associates suggested 
that, because the study received substantial press coverage in 
Washington and other parts of the country, publicity may have 



51 

TABLE 5-4 

Statistical Summary of Aldehyde Concentrations in Various Residential 
Structures (Outdoor Concentrations Very Low) a 



.ocation and Type of 
esidence 

)enver conventional 
Chicago experimental T 
Chicago experimental II 
3 ittsburgh mobile home 1 
Pittsburgh mobile home 2 



Washington conventional I 
Baltimore conventional II 
Washington experimental I 
Baltimore experimental I 
Baltimore experimental II 
Pittsburgh low-rise 1 
Pittsburgh high-rise 1 
Chicago conventional I 
Chicago conventional II 
Pittsburgh low-rise 2 
Baltimore conventional I 
Pittsburgh high-rise 2 
Pittsburgh high-rise 3 
Pittsburgh low-rise 2 



Observed Range of 4-h 
Concentrations, jug/m 

87-615 
140-300 
242-555 
200-938 
136-934 



21-153 
34-150 
10-285 
17-162 
6-122 
51-152 
22-120 
20-190 
10-159 
35-149 
10-300 
76-240 
65-234 
20-102 



14-Day Monitoring Peril 


Mean Con- 


Standard 


centration, 
jag/m 3 


Deviatio 
>ig/nr 


250 


118 


200 


38 


325 


70 


470 


167 


387 


159 


52 


31 


75 


25 


90 


78 


78 


38 


48 


20 


91 


34 


56 


18 


54 


29 


47 


23 


78 


29 


144 


75 


125 


27 


149 


40 


110 


32 



a Reprinted from Moschandreas et al. 



5-16 



52 



C a - 

93 B 



5 



g - 



Si 



Outdoor 
HCHO- 



^ Outdoor 
! aldehydes 



Indoor- 
HCHO 



ru~ 



ro 



! Wndoor 
I f aldehydes 




_n 



240 



Concentration 



FIGURE 5-6 Histogram showing frequency of occurrence of 
formaldehyde and total aliphatic aldehydes at an energy- 
efficient house with 0.2 ach. Single-family house, 
Maryland. Reprinted with permission from Lin et al. 



m 
I 
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53 



54 

motivated people with health problems, some of which were perhaps 
unrelated to formaldehyde, to call on the University of Washington to 
make an investigation. 

Foreign houses (particularly Danish and Swedish) monitored for 
formaldehyde appear to have much higher concentrations than U.S. 
houses. These findings probably reflect differences in house 
construction and, hence, cannot be considered as representative of 
U.S. houses . 

Although use of the Danish studies may not be appropriate for U.S. 
homes, the treatment of Andersen ejt al_. 9 illustrates the many 
variables with which one must oe concerned. He formulated a 
mathematical model that estimates the indoor air concentration of 
formaldehyde. In climate-chamber experiments, Andersen et al. 9 
found the equilibrium concentration of formaldehyde from particleboard 
to be related to temperature, water-vapor concentration in the air, 
ventilation, and the amount of particleboard present. From this work, 
a mathematical model was established for room air concentration of 
formaldehyde. 

When the mathematical formulation was applied to the room-sampling 
results, a correlation coefficient of 0.33 was found between the 
observed and predicted concentration not a particularly good 
predictive ability. The authors then modified the value for the 
adjustable constants by calculating them for each room on the basis of 
monitoring results. The modified values led to a correlation 
coefficient of 0.88 a considerable improvement in predictability. 

Formaldehyde release from interior particleboard occurs at a 
decreasing rate with an increase in product age. Eventually, the rate 
of formaldehyde evolution decreases to an imperceptible point. The 
length of time necessary for the phenomenon to occur (several years) 
depends on the atmospheric conditions to which the board has been 
subjected, as well as the degree of cure of the resin. The more 
unstable groups degrade first, and then the more stable free methylol 
groups. lo l 

Field tests and a mathematical model were used in 1977 to 
determine the half-life of formaldehyde in particleboard typically 
used in Scandinavian home construction; it was about 2 yr when the 
ventilation rate in the home was 0.3 ach (C.D. Hollowell, personal 
communication). Suta 171 * has analyzed the effect of home age on 
formaldehyde concentrations in Danish houses. The study indicated that 
the half-life of formaldehyde may be much longer than 2 yr. These 
data give the following relationship of formaldehyde concentration as 
a function of house age when no corrections are made for other 
pertinent factors, such as the amount of particleboard in the home, 
temperature, humidity, or ventilation: C = 0.50e~' 012A , where C is 
formaldehyde concentration, in parts per million, and A is home age, 
in months. On the basis of this formula, the half-life of 
formaldehyde emission is 58 mo. The difference between half-life 
values derived from the test data and those from house-monitoring may 
result partly from the fact that particleboard is often added to older 
homes for repair and improvement. 

Monitoring data for the 65 randomly selected mobile homes in 
Wisconsin show a similar decrease 'in formaldehyde concentration with 



55 

increasing home age. The reported formaldehyde half-life was 69 mo, 
which is quite similar to that found in the Denmark study. Monitoring 
data on 45 complained-about mobile homes in Wisconsin also showed a 
decrease in formaldehyde concentration with increase in house age; the 
indicated half-life in this sample was 28 mo. When these data are 
combined, the formaldehyde half-life is 53 mo, or approximately 4.4 yr. 

Not all residences are expected to have the same formaldehyde 
concentration. As suggested earlier, variation occurs even in homes 
of the same age, depending on the amount and type of particleboard and 
UF-foam insulation used in the construction, as well as on 
temperature, humidity, and ventilation. For this reason, monitored 
concentrations from a sample of similar homes will be characterized by 
a frequency distribution that can be approximated by a known 
statistical distribution, which, in turn, can be used to estimate the 
range of human exposures to formaldehyde in the residential 
environment. 

The average ambient formaldehyde concentration appears to be 
approximately 0.4 ppm (490 pg/m^) in both mobile homes and 
UF-foam- insulated homes. Few data are available on conventional houses 
that do not contain UF-foam insulation or that were not designed to be 
energy-efficient. The average formaldehyde concentration in 
conventional houses appears to range from 0.01 to 0.1 ppm (12 to 120 
jjg/m^) and may be only slightly higher than outdoor 
concentrations. Houses containing larger amounts of particleboard 
would fall on the high side of this concentration range, and houses 
with no particleboard on the low side. 

Average atmospheric formaldehyde concentrations are generally much 
lower than 0.1 ppm in U.S. cities, as indicated earlier. Examples of 
annual average concentrations are 0.05 ppm in Los Angeles, 6 16e 18 
0.004-0.007 ppm in four New Jersey cities, 1 * 6 0.04 ppm in Wisconsin 
cities (L. Hanrahan, personal communication), and less than 0.03 ppm 
in Raleigh, North Carolina, and Pasadena, California. 79 
Formaldehyde concentrations at four Swiss locations ranged from 0.007 
to 0.014 ppm; these concentrations are about one-fifth the 
corresponding indoor Swiss concentration. 189 In 1951, a mean value 
of 0.004 ppm was reported for mainland Europe. ** 3 



SURFACE WATERS AND DRINKING WATER 

The high solubility of most aldehydes in water results in their 
accumulation in natural bodies of water. Sixteen aldehydes that have 
been identified in natural bodies of water, the names and locations of 
the bodies of water in which they have been found, and their 
concentrations are given in Table 5-6. Acrolein is not included, 
because it has been found only in surface water to which it was 
intentionally introduced. 

Nineteen aldehydes that have been identified in drinking water are 
listed in Table 5-7. Quantitative information on most of these 
aldehydes is unavailable. Some aldehydes in drinking water may be 
produced during water treatment. Chloral, which has been identified 



56 



Aldehyde 
Acetaldehyde 

Benz aldehyde 

Butyraldehyde 
Capraldehyde 

Caproaldehyde 

Caprylaldehyde 

Cinnamaldehyde 

3 , 5-Di-tert-butyl-4- 
hydroxybenzaldehyde 

Dichlorobenz aldehyde 

Dimethylbenzaldehyde 

Enanthaldehyde 

Mesitaldehyde 

2-Methylpropionaldehyde 

Paraldehyde 

Undecyl aldehyde 

Vanillin 



TABLE 5-6 
Aldehydes Identified in Surface Water 

Body of Water and Location 



Mobile River, Ala. 



158 



Pacolet and Encoree River, So. Car. 
Mississippi River, New Orleans, La. 



158 
59a 



Los Angeles River, Los Angeles, Calif 
Unspecified river, Netherlands 

Wisconsin River, Nekoosa, Wis. 

Glatt River, Switzerland 72 
Unspecified reservoir, Netherlands 

Unspecified reservoir, Netherlands 
Unspecified reservoir, Netherlands 
Unspecified reservoir, Netherlands 
Unspecified river, Netherlands 



Unspecified river, Netherlands" 
Unspecified reservoir, Netherlands' 
Unspecified reservoir, Netherlands 
Holston River, Kingsport, Tenn. c 
Delaware River, Torresdale, Pa. 59a 



59a 



Lake Zurich, Switzerland 



62 



Unspecified reservoir, Netherlands 

62 
Lake Superior, Ontario, Canada 



Concentration, 



NR 
NR 
12 

1 
0.3 



NR 
0.1 

0.03 
0.03 
0.03 
0.1 

0.03 

0.1 

0.1 

3 

1 

NR 
0.03 

NR 



1 NR, not reported. 

3 G. J. Piet, personal communication. 



"H. Boyle, personal communication. 



Aldehyde 
Acetaldehyde 



Benzaldehyde 



Butyr aldehyde 
Caproaldehyde 
Chloral 



57 

TABLE 5-7 
Aldehydes Identified in Drinking Water 

Location of Water Plant 

47 



Cinnamalde hyde 
Crotonaldehyde 
Dimethylbenzaldehyde 
Enanthaldehyde 
2-Ethyl but yr aldehyde 

Fur aldehyde 
Isobutyr aldehyde 



Cincinnati, Ohio 
Miami, Fla. 
Ottumwa, Iowa 
Philadelphia, Pa, 



100 



Seattle, Wash. 
Durham, No. Car. 



126 



New Orleans, La. 100 
Grand Forks, No. Dak. 
New York, N.Y. 183 
Voorburg, Netherlands 



183 



Voorburg, Netherlands 
Voorburg, Netherlands 

Cincinnati, Ohio 100 
Grand Forks, No. Dak. 
Philadelphia, Pa. 100 
Seattle, Wash. 10 ? 
New York, N.Y. 100 
Terrebonne Parish, 
Kansas City, Kans. 

Voorburg, Netherlands 
Unspecified 158 
Voorburg, Netherlands 

i 

Voorburg, Netherlands 

New York, N.Y. 100 
Grand Forks, No, Dak. 
Lawrence, Mass. 
Terrebonne Parish, La. 

Chicago, Ill. 59a 
Prague, Czechoslovakia 



158 



100 



100 



100 



100 



144 



Concentration, 



NR 

NR 

NR 

0.1 

0.1 

NR 

0.03 
NR 
NR 
0.3 

0.1 
0.03 

2 

0.01 

5 

3.5 

0.02 

1 

NR 

0.005-0.03 
NR 

0.03-0.1 
0.03 

0.05 
0.02 
0.04 
0.01 

2 
0.13 



58 



Aldehyde 

I sovaler aldehyde 



Methacrolein 
2-Methylpropionaldehyde 



3-Methylvaleraldehyde 

Paraldehyde 

Propionaldehyde 



TABLE 5-7 (continued) 

Location of Water Plant 
.47 



Cincinnati, Ohio 
Miami, Fla. 47 
Ottumwa, Iowa 
Philadelphia, Pa, 
Seattle, Wash. 47 
Durham, No. Car. 
New Orleans, La. 

Unspecified 158 

Cincinnati, Ohio 
Miami, Fla. 47 
Ottumwa, Iowa 
Philadelphia, Pa 
Seattle, Wash. 47 
Durham, No. Car. 

Ottumwa, Iowa 100 



47 



47 
184 



47 



47 



126 



Zurich, Switzerland 
.47 



75 



Cincinnati, Ohio 
Miami, Fla. 47 
Ottumwa, Iowa 
Philadelphia, 
Seattle, Wash. 
Durham, No. Car. 



47 



126 



Valeraldehyde 



Ottumwa, Iowa 



100 



Concentration 



NR 
NR 
NR 
NR 
NR 
NR 
NR 

NR 

NR 
NR 
NR 
NR 
NR 
NR 

1 
NR 

NR 
NR 
NR 
NR 
NR 
NR 

0.5 



NR, not reported 



. J. Piet, personal communication. 



59 

in the drinking water of seven U.S. cities, is thought to be formed 
during chlorination for water purification. 100 

SOURCES OF DIRECT EMISSION OP ALDEHYDES IN AMBIENT AIR 
INDUSTRIAL OPERATIONS 
Aldehyde Manufacturing Plants 

The leakage of aldehydes into the atmosphere may occur in the 
operation of industrial plants that manufacture the aldehydes. 
Morris ^ 3 1** and Lovell 8 have estimated formaldehyde losses to 
the environment to be 0.4 g/1,000 g of product formed in solution. 
The atmospheric emission of formaldehyde from manufacturing processes 
in the United States can be roughly estimated at about 6 x 10 
Ib/yr. These losses usually occur at the following locations within 
the plants: 

The vent stream from the water absorber used for the recove 
of formaldehyde and methanol usually contains carbon dioxide, carbon 
monoxide, hydrogen, water vapor, nitrogen (if air is used), and trac 
amounts of formaldehyde, methanol, and some byproducts. The absorbe 
can be built and operated to recover formaldehyde so effectively tha 
the exit gas stream is sometimes exhausted directly into the 
atmosphere. Other formaldehyde producers use slightly less efficien 
and cheaper absorbers with lower operating costs and use the exhaust 
streams as supplemental fuel in the furnaces of their power stations 
because the streams often have appreciable fuel values. In another 
alternative, the vent stream from the absorber can be sent to a 
flare. Almost complete oxidation of formaldehyde, methanol, and 
carbon monoxide occurs in both a furnace and a flare, so the exhaust 
gas stream from the formaldehyde unit contains little formaldehyde. 

The vent stream from the top of the product fractionator us 
to prepare specification-grade product solution can be sent as neede 
to a flare, a furnace, or an absorber to reduce the formaldehyde 
content. 

Intermittent gaseous emission that occurs during plant 
startup or shutdown is sometimes sent to a flare, the furnace, or a 
small water absorber to reduce the formaldehyde content. 

Intermittent losses that occur at pump seals, from storage 
tanks, or at valves are sometimes controlled with portable gas blowe 
used in connection with small absorbers. 

Each industrial plant uses various combinations of water 
absorbers, flares, furnaces, and catalytic incinerators to maintain 
formaldehyde concentrations in the ambient air of the plant at less 
than 3 ppm as the time-weighted average for an 8-h workshift. This 
the maximal permissible concentration set by the Occupational Safety 
and Health Administration in 1979. The EPA does not have an ambient 
air standard for formaldehyde. 



60 

Information on emission from industrial plants producing the 
higher aldehydes is very limited. It is probably reasonable to assume 
^that the percentages of the more volatile aldehydes such as 
acetaldehyde/ acrolein, and propionaldehyde lost into the atmosphere 
are comparable with those reported for formaldehyde. 



Other Industrial Sources 

Shackleford and Keith 158 have reported that aldehydes occur in 
the effluent water streams from several types of industrial plants. 
Formaldehyde, acetaldehyde, acrolein, paraldehyde, sorbaldehyde, and 
syringaldehyde have been detected in unidentified chemical plants in 
rather scattered areas of this country. Aldehydes identified in the 
effluent from some sewage plants include acetaldehyde, benzaldehyde, 
crotonaldehyde , isovaler aldehyde, 2-methylpropionaldehyde, and 
salicylaldehyde. It is not known whether the aldehydes in these 
sewage plants were produced by microbial or chemical means or were in 
the feedstock to the sewage plants derived from various industrial 
plants . 

Acrolein, anisaldehyde, benzaldehyde, salicylaldehyde, 
syringaldehyde, vanillin, and veratr aldehyde have been detected in the 
effluent from paper mills. Benzaldehyde has been identified in the 
aqueous waste from textile mills. Some of these aldehydes probably 
form as a result of reactions involving wood or cellulose. 

Fish-culture activities are also a source of formaldehyde in the 
aquatic environment. Formalin (aqueous solution of formaldehyde) is 
one of the most widely and frequently used chemical agents for 
treating fish with fungal or ectoparasitic infections. Treatment 
entails exposing the fish to formaldehyde at up to 250 mg/L of 
solution in ponds, raceways, or tanks. After use, these formaldehyde 
solutions are often discharged into the normal hatchery effluent 
stream from both private and government-owned fish hatcheries. 

Anisaldehyde has been detected in the aqueous effluent of a pilot 
plant being used for coal gasification. This suggests that, when 
commercial coal-gasification plants are built, they may contribute to 
aldehyde effluent. 

Table 5-8 shows reported aldehyde emission from various industrial 
sources, as collected by Stahl. 16B 



Combustion 

Combustion leads to both the direct and the indirect accumulation 
of aldehydes in the atmosphere of metropolitan areas. Aldehydes are 
present in at least trace amounts in the exhaust gases from 
combustion. In addition, there is often, if not always, some unburned 
hydrocarbon that escapes to the surroundings. As discussed later, 
this hydrocarbon oxidizes rapidly in the atmosphere to form aldehydes 
and other oxygenated products. Emission from transportation vehicles, 
power plants burning fossil fuels, home and industrial furnaces, 



61 

TABLE 5-8 
Reported Aldehyde Emission from Various Sources 3 

Aldehyde Emission 
Source __ (as formaldehyde) 

Amberglass manufacture 

3 

Regenerative furnace, gas fired 8,400;ig/m 

Brakeshoe debonding 

(single-chamber oven) 0.10 Ib/h 

Core ovens 

Direct gas fired (phenolic resin 

binder from oven) 62,400 >ig/ra 

Direct gas fired (linseed oil core 

binder from afterburner <12,000 >ag/m 

Indirect electric (linseed oil core 

binder from oven) 189,600 jig/m 



(from afterburner) <22,800 

Insulated wire reclaiming, covering 
Rubber 5/8" o.d. 

O 

Secondary burner off 126,000 >ig/nr 

o 

Secondary burner on b,OUU ug/m 

Cotton rubber plastic 3/8-5/8" o.d. 

Secondary burner off 10,800 to 

43,200 jig/in" 3 

o 

Secondary burner on 4,800 ug/m 

Meat smokehouses 

Pressure mixing burner 

Afterburner inlet 0.04 Ib/h 

Afterburner outlet 0.22 Ib/h 



62 



TABLE 5-8 (continued) 



Source 

Mineral wool production 
Blow chambers 
Curing ovens 

Catalytic afterburner inlet 
Catalytic afterburner outlet 
Direct flame afterburner inlet 
Direct flame afterburner outlet 
Wool coolers 
Litho oven inlet 
Litho oven outlet 
Litho oven outlet 
Paint bake oven 

Nozzle mixing burner 
Afterburner inlet 
Afterburner outlet 
Atmospheric burner 

Catalytic afterburner inlet 
Catalytic afterburner outlet 
Premix burner 

Catalytic afterburner inlet 
Catalytic afterburner outlet 
Phthalic acid plant 



Aldehyde Emission 
(as formaldehyde) 



109 ug/m 3 

1.90 Ib/h 
0.90 Ib/h 
2.20 Ib/h 
0.94 Ib/h 
32 ug/m 3 
120 Mg/m 3 
32,880 ug/m 3 
4, 680 ug/m 3 



0.19 Ib/h 
0.03 Ib/h 

0.07 Ib/h 
0.31 Ib/h 

0.3 to 0.4 Ib/h 
0.2 to 0.5 Ib/h 
135,600 ug/m 3 



63 



TABLE 5-8 (continued) 

Source 

Multijet burner 

Afterburner inlet 
Afterburner outlet 

Meat smokehouse effluent, gas fired 
boiler firebox as "afterburner" 

Water tube, 426 hp 

Afterburner inlet 

Afterburner outlet 
Water tube, 268 hp 

Afterburner inlet 

Afterburner outlet 
Water tube, 200 hp 

Afterburner inlet 

Afterburner outlet 
Locomotive, 113 hp 

Afterburner inlet 

Afterburner outlet 
HRT, 150 hp 

Afterburner inlet 

Afterburner outlet 
Meat smokehouse exhaust 

Gas fired afterburner inlet 
Gas fired afterburner outlet 
Electrical precipitation system inlet 
Electrical precipitation system outlet 



Aldehyde Emissic 
(as formaldehyde 



0.49 Ib/h 
0.22 Ib/h 



0.22 Ib/h 
0.09 Ib/h 

0.39 Ib/h 
0.40 Ib/h 

0.39 Ib/h 
0.30 Ib/h 

0.03 Ib/h 
0.0 Ib/h 

0.03 Ib/h 
0.18 Ib/h 

104,400 ug/ 
40,200 ug/ 
88,800 ug/ 
56,400 ug/ 



64 



TABLE 5-8 (continued) 



Source 



Phthalic anhydride production unit 
(multiple burner) 

Afterburner inlet 
Afterburner outlet 

Reclaiming of electrical windings 
(single chamber incinerator) 

100 hp generator starter 
14 pole pieces 
Auto armatures 

Auto field coils (multiple 
chamber) 

Auto field coils afterburner 
14 generator pole pieces 
Varnish cooking kettles 

Four nozzle mixing burner 

Afterburner inlet 

Afterburner outlet 
Inspirator burner 

Afterburner inlet 

Afterburner outlet 
Webb press 



Aldehyde Emission 
(as formaldehyde) 



1.75 Ib/h 
0.43 Ib/h 

0.08 Ib/h 

0.08 Ib/h 

0.13 to 0.29 Ib/h 

0.49 Ib/h 
0.08 Ib/h 
0.08 Ib/h 



0.30 Ib/h 
0.11 Ib/h 

0.29 Ib/h 
0.02 Ib/h 
480 ;ig/m 3 
360 pg/m 3 
480 ;ig/ni 3 
1,920 jig/nT 3 



a Reprinted from Stahl. 168 



65 



garbage fires, and bonfires contributes to the rather high aldehyde 
concentrations in metropolitan areas. General reviews of the amounts 
and fate of aldehydes in the atmosphere have recently been issued. 115 



Transportation Vehicles 

Transportation vehicles are important and possibly at times the 
predominant contributors to both aldehyde and hydrocarbon emission in 
some metropolitan areas. Much valuable information on emission from 
automobiles, trucks, buses, airplanes, etc., has accumulated in the 
last few years. The exhausts of various automobiles powered with 
gasoline engines have been collected by General Motors Corp. Tables 
5-9 and 5-10 indicate the relative concentrations of the specific 
aldehydes identified in the exhaust gases from automobiles without and 
with catalytic converters, respectively. Formaldehyde is almost 
always the predominant aldehyde emitted, but at least 11 others have 
been identified, including at least three aromatic aldehydes. As 
discussed later, the amounts of aromatic aldehydes produced depend 
significantly on the aromatic hydrocarbon content of the gasoline used, 

Several factors affect aldehyde and unburned-hydrocarbon 
concentrations in automotive emission. The most important ones are 
discussed below. 

Operation of Gasoline Engines and Catalytic Converters. 
Automotive manufacturers are under federal mandate to reduce the total 
hydrocarbon emission to 0.41 g/mile or less within the next several 
years. There is no question but that catalytic converters and other 
recent changes in motor-vehicle design and operation have resulted in 
substantial reductions in aldehyde and unburned-hydrocarbon emission. 
For example, higher air-to-fuel ratios are provided in modern 
engines. In 1971, the Los Angeles Air Pollution Control District 
(APCD) estimated that motor vehicles contributed about two-thirds of 
the total hydrocarbon emission inventories to the atmosphere of the 
Los Angeles area. By 1975, with the increased use of catalytic 
converters, the Southern California Air Pollution Control District 
(formerly the Los Angeles APCD) estimated that motor vehicles 
contributed less than half. 

Newer cars equipped with catalytic converters often emit aldehydes 
at about 20-60 mg/mile; older cars without the more modern control 
devices emit aldehydes at about 70-300 mg/mile. Automobiles also emit 
a variety of paraffinic, unsaturated, and aromatic hydrocarbons. 
Jackson 91 found an average of 2.45 g/mile for 19,70-1974 automobiles 
not equipped with catalytic converters. Hydrocarbons are emitted by 
1974-1975 cars equipped with three types of catalytic converters at ai 
average of 0.48-0.65 g/mile. Recently, Cadle, Nebel, and Williams 32 
reported emission rates for catalytic and noncatalytic automobiles 
similar to these values. 

As more vehicles become equipped with catalytic converters, motor 
vehicles will probably emit less aldehyde and unburned hydrocarbon. 

The following factors also affect emission: 



66 



O 

O 



CO 

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cfl 

u 

4J 
CO 



Cfl 
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o 





4J 
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3 
cti 

fl 



-n 

3 



ON 

m 





JO 


m 



o 



o 



O 
O 



o 

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JS 






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67 

TABLE 5-10 

Exhaust Aldehyde Composition: Gasoline Exhaust from Catalyst Cars a 
Concentration, mole % 



Aldehyde 


BOM D BOM*- 


BOM 








Formaldehyde 


55 


.2 


36. 


5 


35. 


1 


42.2 


63.7 


62. 


1 


78.2 


Ace t aldehyde 


25 


.5 


34. 


9 


40. 


8 


23.5 


14.9 


17. 


5 


13.3 


Propionaldehyde 


1 


.0 


3. 


6 


4. 


2 


2.4 


15.1 


2. 


6 


4.6' 


Acrolein 







1. 


1 


ND 




ND 


0.1 


0. 


4 


ND 


Crotonaldehyde 


- 


- 


























Methacrolein 







4. 


1 


7. 


1 


2.4 


ND 


ND 


ND 


Benzaldehyde 


10 


.1 


11. 


3 


7. 


5 


17.0 


3.7 


12. 


2 


2.3 


Tolualdehydes 


1 


.2 


2. 


3 


1. 


3 


2.2 


0.9 


2. 


3 


0.5 


Ethyl benzaldehyde 


2 


.5 


3. 


2 


2. 


9 


6.0 


0.7 


0. 


6 


0.3 


Lj j-v tl T f\ \J 


4 


.5 


3. 





1. 


1 


4.3 


0.9 


2. 


3 


0.9 


9 10 
























Total 


100 




100 




100 




100 


100 


100 




100 


Driving Cycle 


7 -mode 


72-FTP 


72 FTP 



a j. M. Heuss, personal communication. 
Pt mono. oxid. catalyst. 
Pt mono. oxid. catalyst; 3 gasolines. 
^Dual RO catalysts; same 3 gasolines. 
e !975 Plymouth Fury. 



68 

Age, condition, and degree of tuning or adjustment of the 
engine engines require tuning and maintenance, if they are to have 
low emission rates. 

Converter replacement catalytic converters age and must 
eventually be replaced, if they are to maintain sufficiently low 
emission rates. 

Design of engine engine types in different cars sometimes 

result in quite different emission rates. 

Temperature of ambient air 75 F was found to result in lower 
aldehyde emission for some engines, compared with 25F or 95F; and 
starting a cold engine generally results in high aldehyde emission 
rates. 

Composition of Gasoline or Liquid Fuel. The aromatic-compound 
content of gasoline has an important effect on the benzaldehyde 
content of the exhaust. 1 2 Little or no benzaldehyde was produced 
from a gasoline free of aromatic compounds, but the amount of 
benzaldehyde increased linearly with increased aromatic-compound 
content. With a 100% aromatic fuel, the ratio of formaldehyde to 
benzaldehyde was about 3:1; the total aldehyde content of the exhaust 
gases from the engine was, however, nearly constant, regardless of the 
aromatic-compound content of the gasoline. Ninomiya and Golovoy 1 " 9 
found that rather large amounts of benzaldehyde were produced when 
toluene (an aromatic hydrocarbon) was blended into gasoline. 

Gasolines produced by different refineries or produced at 
different times of the year often contain large variations in the 
amounts of specific hydrocarbons. These hydrocarbons may be grouped 
into three families: the alkanes (paraffinic hydrocarbons), the 
alkenes (olefinic hydrocarbons), and the aromatic hydrocarbons. 
Higher-quality or premium gasolines usually have more aromatic 
hydrocarbons and/or trimethylpentanes (highly branched Cg alkanes) . 
Especially in the recent past, they also generally contained more 
antiknock compounds, such as tetraethyl and tetramethyl lead. 
Furthermore, winter-grade gasolines as a rule contain more volatile 
hydrocarbons, such as butanes, to provide quicker starting. In tests 
by Bykowski 29 of gasohol (blends of 90% gasoline and 10% ethanol) , 
summer-grade gasohol for two types of American automobiles emitted 
about 50-60% more aldehydes than winter-grade gasohol. The 
hydrocarbon composition of the fuel clearly has some effect on the 
type and amount of emission, but only preliminary data are available. 

Within the last few years, there have been extensive efforts to 
develop blends of gasolines that contain various oxygenated 
hydrocarbons, including the following: 

Ethanol (ethyl alcohol) that is blended with gasoline at 
5-20% these blends are generally referred to as gasohol; the main 
objective in using ethanol is to develop liquid fuels obtainable from 
grains of cellulose-containing materials (such as wood, straw, and 
cornstalks) that are grown in this country. 

Methanol (methyl alcohol) this has also been tested rather 
extensively and is sometimes confused with the gasohol approach; 



69 

methanol can be obtained from natural gas, petroleum/ coal, and wood; 
it is now used as a fuel for some racing vehicles. 

Methyl-tert-butyl ether (MTBE) MTBE is being blended with 
gasoline at 5-20% by several oil companies; it results in 
substantially higher octane ratings and is thought by many persons 
knowledgeable about gasoline to have a bright future. 

Gasoline and gasohol have been compared in several types of 
automobiles, but the results are inconclusive. Bykowski 29 found 
lower aldehyde emission rates in one automobile when gasohol was used 
but the opposite in another automobile. Chui, Anderson, and Baker 1 * 5 
made a rather large number of tests with gasohol blends containing 2G 
ethanol in several Brazilian automobiles. There were small but 
significant increases in aldehyde emission from ethanol-gasoline 
blends when the engines operated at low load. Differences at normal 
load, however, were small and perhaps insignificant. A considerable 
number of investigations have compared methanol-gasoline blends and 
pure gasoline. In general, slightly more aldehyde was emitted from 
methanol-containing fuels; 13 * 7 ll>8 some of the increase occurred in 
tests at higher compression ratios that simultaneously resulted in 
increased engine efficiencies. One of the major advantages of 
methanol is that it produces higher octane blends that can be burned 
at high compression ratios. It has been suggested 1118 that aldehyde 
emission can be markedly reduced by proper adjustment of the 
air-to-fuel ratio and by spark-advance settings. 

Preliminary information has also been published on the use of 
MTBE-gasoline blends. Emission from the burning of such blends is 
comparable with that from unblended gasolines, except for somewhat 
higher aldehyde and isobutylene emission from the blended fuel. 81 
It is thought that emission problems of the blends can be made at 
least comparable with those of unblended gasolines by proper engine 
adjustment and minor changes in the operation of catalytic convertei 

There is need for continued testing of aldehyde emission from 
automobiles as the use of gasohol and other new fuel blends increase 
although present evidence suggests that proper use of catalytic 
converters and other devices may control this emission quite well. 

Type of Engine. Several engines have been considered as 
alternatives to the conventional piston-cylinder gasoline engine us< 
almost exclusively for many years in automobiles. Such engines 
include the diesel, stratif ied-charge (PROCO) , and rotary engines, 
with the conventional gasoline engine, rather large variations in 
performance occur from engine to engine, including aldehyde and oth< 
undesirable emission. Such differences are caused by numerous 
variables, including engine design and operation, fuel composition . 
quality, and use of or failure to use a catalytic converter. 
Comparisons of various engines have been conducted by most if not a 
major automobile manufacturers and oil companies, universities, 
research organizations, and government laboratories. 

The following comparisons of diesel and gasoline engines are 
applicable: 



70 

Diesel engines emit more hydrocarbon and aldehyde than 
gasoline engines equipped with catalytic converters. They also emit 
appreciably more particulate material. The relative importance of 
specific hydrocarbons and aldehydes in the emission from diesel 
engines tends to be quite different from the relative importance of 
those from conventional gasoline engines. 

In many cases, the aldehydes emitted from diesel engines have 
higher molecular weights than those from gasoline engines. 
Isobutyraldehyde is sometimes the most important aldehyde on a weight 
basis. 152 1SS Over twice as much isobutyraldehyde as formaldehyde 
was emitted from one engine. In another and more typical case, 
formaldehyde emission was higher. The increased yield of the higher 
aliphatic aldehydes from diesel-fuel combustion probably results from 
the dominance of the higher-molecular-weight paraffinic hydrocarbons 
in this fuel. Benzaldehyde normally is either not detected in the 
emission from diesel engines or present in only small amounts; most 
diesel fuels contain little or no aromatic hydrocarbon. 

Emission from a stratif ied-charge (PROCO) engine and emission from 
a conventional gasoline engine have been compared to at least a 
limited extent. In two comparisons, the stratif ied-charge engine 
emitted more aldehyde than a regular gasoline engine. 29 125 In two 
others, the opposite was reported (Bachman and Kayle; 12 J.M. Heuss, 
personal communication) : two Honda CVCC engines emitted considerably 
less aldehyde. Insufficient information is available to draw any 
generalized conclusions relative to the aldehyde emission of the two 
types of gasoline engines. 

There are limited data comparing a rotary engine such as was used 
at one time in Mazda cars with conventional gasoline engines 
(Bykowski; 29 Heuss, personal communication). The rotary engine 
emitted more aldehyde than the conventional engines in at least three 
comparisons; in two cases, the differences were large. 

In summary, we may estimate that direct aldehyde emission from all 

O 

vehicles in the United States amounts to about 2.6 x 10 Ib/yr. 
Another 10 9 Ib/yr is probably generated from the atmospheric 
oxidation of the hydrocarbon emitted by these vehicles. These 
estimates are very approximate and may be in error by as much as a 
factor of 3.* 



Other Combustion Processes 

Fossil-fueled power plants emit several undesirable materials to 
the atmosphere, including aldehydes, as shown in Table 5-11. The 



*The following assumptions have been made in deriving these 
estimates: 120 x 10 gal of gasoline are consumed per year; travel 
amounts to 144 x 10^ miles/yr, with an average gasoline mileage of 
12 miles/gal; hydrocarbon is emitted at 0.41 g/mile, as mandated for 
the future; and 20% of the emission is aldehydes, and 80%, hydrocarbon. 



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72 

amount and type of such emission vary greatly between plants, but the 
lowest rates of formaldehyde emission occurred in some coal-burning 
plants. In 1978, Natusch 137 reported rather limited data from power 
plants using coal, oil, and natural gas. Coal-fired furnaces emitted 
the most particles, the most carbon monoxide, and the least aldehyde 
(reported as formaldehyde). Aldehyde emission by coal-, oil-, and 
natural-gas-fired furnaces was reported to be 0.002, 0.1, and 0.2 Ib 
from 1,000 Ib of fuel. If the results of Natusch are average values 
and if the consumption data of the U.S. Department of Energy for coal, 
oil, and natural-gas consumption in power plants are used, the amount 
of aldehyde emitted from power plants in the United States is 
estimated to be approximately 50 million pounds per year (see Table 
5-12) . The unburned hydrocarbon emitted may lead to the eventual 
formation of 10-20 times more aldehyde. Large changes have occurred 
in the last 10-20 yr in the design and operation of fossil-fueled 
power plants. As a general rule, the major emphasis has been on 
increased energy efficiency. The results probably produce more 
complete combustion and decreased aldehyde concentrations, although 
specific data to support this hypothesis are not available. 

Sulfur dioxide is considered by many to be a more obnoxious 
emission from oil- and coal-burning plans than aldehyde. Natusch 137 
pointed out that the polycyclic organic materials formed to a small 
extent, particularly from coal-fired furnaces, were especially 
critical, in that such materials are generally considered to be 
carcinogens. 

A variety of aldehydes have been identified as products of forest 
fires (Table 5-13) . Bonfires and garbage fires also produce aldehydes 
and other undesirable byproducts. The amounts emitted obviously 
depend on the size of the fire, i.e., the amount of material burned 
(Table 5-14) . In most cases, detrimental effects of such fires are 
limited to the immediate area of the fire. 

The combustion of tobacco in the process of cigarette-smoking also 
generates a variety of aldehydes. This is an important source of 
aldehydes only in the indoor environment, and it is discussed in more 
detail later in this chapter. 



VEGETATION 

Plants in general have the ability to release volatile compounds 
into the air through their stomata and cuticle. Of these compounds, 
carbon dioxide, oxygen, and water have been studied in detail, owing 
to their metabolic relevance. Attention has recently turned to plants 
as a source of hydrocarbons important enough to affect air quality. 
Terpene diffused from forest trees has been the principal compound of 
concern; 150 aldehydes, in comparison, have received little attention. 

There is ample evidence of the natural occurrence of aldehydes in 
plants. Schauenstein et^al^. 153 noted that aldehydes are widely 
distributed in fruits, imparting a characteristic aroma and flavor to 
pineapple, apple, grapefruit, lime, banana, pear, peach, lemon, 
blackcurrant, strawberry, orange, grape, and raspberry. Strawberry 



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74 



TABLE 5-13 
Aldehydes Emitted by Forest Fires a 



Aliphatic 
Formaldehyde 
Acetaldehyde 
Propanal 



Aromatic 
Vanillin 
Conifer aldehyde 
Syringaldehyde 
Sinapaldehyde 



Is o but anal 



Olefinic 
Acrolein 



Cyclic 

Furfural 

5-Methylfurfural 



a l)ata from Graedel. 73 



75 



TABLE 5-14 
Gaseous Emission from Open Burning a 



Gaseous Emission, Ib/ton of material 
initially present 



Test 
No. 


Material Burned 
Municipal refuse 


CO,, 
1,250 


CO 


hC b 


Formaldehyde 
0.095 


Organ 
Acids' 

14 


1 


90 


30 


2 




1,210 


80 


30 


0.094 


16 


Avg. 




1,230 


85 


30 


0.095 


15 


3 


Landscape refuse 


860 


80 


35 


0.005 


18 


4 




550 


50 


25 


0.006 


8 


Avg. 




700 


65 


30 


0.006 


13 


5 


Automobile 
components 


1,500 


125 


30 


0.030 


16 



a Reprinted with permission from Gerstle and Keranitz. 

Gaseous hydrocarbons expressed as methane. 
Expressed as acetic acid. 



70 



76 

and pear have an especially high aldehyde content 13-18 rag/kg. Some 
species contain three carbonyl compounds f others as many as 20 (Table 
5-15); 2-trans-hexenal (2TH) is the most common. Schauenstein et al. 
speculated that the unusually wide distribution of 2TH indicates that 
it probably is formed during the processing of the fruit. According 
to their interpretation, some aldehyde in apple and fruit ^uices is 
formed biogenically in the fruit/ and some of the remainder is 
produced by enzymatic and nonenzymatic reactions during processing. 
Vegetables are not without their share of aldehydes. 167 
Acetaldehyde, propionaldehyde , isobutyraldehyde, and butyraldehyde 
have been detected in beans, broccoli, brussels sprout, cabbage, 
carrot, cauliflower, celery, cucumber, lettuce, onion, potato , and 
soybean . 

Woody species also contain aldehydes, but there is disagreement as 
to whether they occur in healthy, as well as in injured, tissue. 
According to Schauenstein et: a!L. , 153 one report stated that 2TH was 
emitted by Robin ia pseudoacacia in the absence of injury when the 
plant was enclosed within a plastic bag for 12 h. More numerous 
reports cite the capacity for formation of 2TH in injured trees, such 
as Ginkgo biloba, Albizia julibrissin, and Ailanthus glandulosa. It 
has been suggested that the biosynthesis of aldehydes is a defense 
against biologic attack, for example, in the resistance shown by 
ginkgo to fungi. 123 

In the course of inquiry into the possible etiologic factors of 
nasopharyngeal tumors among the Chinese and Kenyans, Gibbard and 
Schoenthal 71 made a semiquantitative measurement of sinapylaldehyde 
and related aldehydes in the wood of eight angiosperms and two 
gymnosperras. The aldehyde content varied according to species, with 
Eucalyptus sp. and Fagus sylvatica having the highest and Juniperus 
procera and Larix decidua the lowest content (Table 5-16). 

There is some information on the location of aldehydes in plant 
tissue. 1S3 A report by Lamberton and Redcliffe established that the 
long-chain aldehydes occur in cuticular plant waxes. On measuring the 
aldehyde content as a percentage of total lipids, they found a range 
from 0.2% in purple loosestrife (Lythrum salicaria) to 14.3% in 
cranberry (Table 5-17) . Apparently, the distribution pattern of 
aldehydes is so characteristic for a species that it may have value in 
taxonomic studies. 

Aldehydes emanating from vegetation have been detected in ambient 
air. 73 Thirty-six plant volatiles including aliphatic, olefinic, 
aromatic, and cyclic aldehydes have been cited by Graedel (Table 5-18). 

When plant material is burned either deliberately for disposal of 
agricultural waste or unintentionally as in forest fires, the increase 
in aldehyde emission may become significant. Because the nature of 
the plant material and the conditions of the burning can vary widely, 
it is difficult to characterize the emission. In a special experiment 
with a tower that simulated field conditions, Darley et al. 51 
compared emission from the three principal types of agricultural waste 
in the San Francisco Bay area. The number of pounds of total 
hydrocarbon emitted per ton of plant material was 9.7 for fruit 
prunings, 14.5 for barley straw, and 4.4 for native brush. Aldehydes 



Pineapple 

formaldehyde 
acetaldehyde 
furfural 

Apple 

formaldehyde 

acetaldehyde 

propanal 

1-butanal 

pentanal 

hexanal 

2-hexenal 

furfural 

C 24-30 a l deh y des 
Grapefruit 

acetaldehyde 

citral 

C 7_H aldehydes 

Lime 

octanal 

nonanal 

citral 

dodecanal 

furfural 

Banana 

acetaldehyde 

1-pentanal 

2-hexenal 

C 24 C 26' C 28' 

c 29 , c 30 , c 31 , 

C^2 aldehydes 
Peach 

acetaldehyde 
benzaldehyde 
furfural 

C 24> C 26 

C aldehydes 



77 

TABLE 5-15 

Carbonyl Compounds in Various Fruits 3 
Pear Orange 



acetaldehyde 

propanal 

2-hexenal 

Lemon 

heptanal 

octanal 

nonanal 

decanal 

undecanal 

dodecanal 

C^3_17 aldehydes 

citral 

neral 

geranial 

citronellal 

Blackcurrant 

acetaldehyde 

butanal 

pentanal 

hexanal 

2-hexenal 

benzaldehyde 

Strawberry 

acetaldehyde 

propanal 

2-propenal 

2-butenal 

2-pentenal 

hexanal 

3-cis-hexenal 

heptanal 

benzaldehyde 

furfural 

methylfurf ural 



acetaldehyde 

pentanal 

hexanal 

2-hexenal 

heptanal 

octanal 

octenal 

nonanal 

decanal 

undecanal 

citral 

neral 

geranial 

dodecanal 

01, 6-substituted acroleins 

C 24' C 26 ' ^28 C 30 
Grape 

acetaldehyde 

butanal 

hexanal 

2-hexenal 

benzaldehyde 

Raspberry 

acetaldehyde 

propanal 

2-propenal 

2-methylpropenal 

2-pentenal 

2-hexenal 

3-cis-hexenal 

benzaldehyde 

furfural 

methyl furfural 



a 1 ^ 

Reprinted with permission from Schauenstein et al. 

alkenals have 2-trans configuration. 



Unless otherwise stated, 



78 



TABLE 5-16 

.a 



Yields of Aldehydes in Wood of Various Tree Species' 



Aldehyde Yield, ;ig/g 



Tree Sinapyl Syringic Coniferyl Vanillin 

Eucalyptus sp. J,OOU 3,000 1M) 100 

Fagus sylvatica L. (beech) 800 800 250 250 

Tectona grandis (teak) 700 500 600 450 

Santalum album (sandalwood) 600 500 300 200 

Quercus robur L. (oak) 500 600 250 200 

Chinese incense 500 600 250 250 

Indian incense 100 200 100 5U 

Cocos nucifera L. (coconut) 300 500 3UO 300 

Juniperus procera Hochst 450 bOO 

Larix decidua (larch) bOO bUO 

Reprinted with permission from Gibbard and Schoental.^ 1 



79 



f"** QO ON 
04 m 



rt 00 

6 o 



o 
S - 



ao <N irt 



cfl 

CO 

u 

H 



IS O 



I 

LO 



-d 

fi 



C/3 

s 

H 

CO 
0) 



01 
-d 






rt o* 

m oo 

t^ 



^o n rn oo 



OO O 



-n 

n 
H 



s Distribution of aldeh] 
il 

C 3 4 C C M 


* 


(N 


>n 

r* 

^r 




00 

TT 




6 




>* 

ON 
en 

en 


>M 

'? 
O 

ON 
CS 


%^- i^- 

ft Tf 

VO 00 
CN 

* 
tN 


O iS 
























f 9? 


o 


^ 


^ 




00 


10 


m 




CN 


NO 


, 


^Sj* 


Wl 


w 


~ 




* 


6 


rn 




O 





ON 






J 
























5 
















O 


x- \ 






^ 

r\ 


2 




/ N 




3 









J 

> 


8 


(Axum uttntm) 


bane 
icynum androsaemifi 


an hemp 
ycynum cannabuwm 


& 

1 

a 

V 


>horbia cyparkuas L. 


^ 
X 

3 

a 

J 


1 

s 
1 


le loosestrife 


*~ \ 
J 

1 

E 
1 


ten {Chenopodtum at 


pass (Lolum perenm 





^1 
SI 



cd 
J=i 
a 

V3 



^ 
m 

PI 
o 

H 
CO 
CO 



OJ 
Pu 

x: 

4-1 



d 
ai 

4J 

c 

H 
^ 
P- 

cu 
od 
cd 



80 



TABLE 5-18 
Aldehydes Emitted from Natural Plant Sources 3 



Alipnatic 

Formaldehyde 

Acetaldehyde 

Propanal 

i- But anal 

Isobutanal 

ji-Pentanal 

Isopentanal 

Hexanal 

He pt anal 

Octanal 

Nonanal 

Decanal 

Unde canal 

Te trade canal 



Aromatic 

Be nz aldehyde 
Cuminaldehyde 
Dihydrocuminaldehyde 

Phenylpropanal 
Cinnamaldenyde 
_p_-Hydroxybenzaldehyde 
Anisaldehyde 
j)-Me thoxycinnamaldehyde 
Piperonal 
Vanillin 
Veratraldehyde 
Conifer aldehyde 
Eve rnic aldehyde 



Olefinic 

l-Hexen-2-al 

trans-2-Hexenal 

3, 7-Dimethyl-2, b-octadien-1-al 

3 , 7-Dimethyl-b-octen-l-al 

4-Hydroxy- 3 , 7-dimethyl-6-octen-l-al 

2, b-Nonaldien-1-al 



Cyclic 

Furfural 
Safranal 



a Data from Graedel. 73 



\ 



81 

were not mentioned specifically. In the burning of landscape refuse 
(lawn clippings, leaves, and tree branches), Gerstle and Kemnitz 70 
reported 30 Ib of hydrocarbons and only 0.005 Ib of formaldehyde per 
ton of material. Combustion of the same amounts of municipal refuse 
and automobile components yielded about the same amount (30 Ib) of 
hydrocarbon, but an increase in formaldehyde from 0.005 Ib/ton to 
0.095 and 0.030 Ib/ton, respectively. 



INDOOR SOURCES OF ALDEHYDES 

Aldehydes enter the indoor environment through infiltration of 
outdoor air and from a variety of sources within the indoor 
environment itself. Indoor sources include aldehyde-containing 
building materials, combustion appliances, tobacco smoke, and a large 
variety of consumer products. Measurements of aldehydes in the indoor 
environment have focused almost exclusively on formaldehyde. In 
general, indoor formaldehyde concentrations exceed outdoor 
concentrations. The contribution of formaldehyde in outdoor air to 
indoor formaldehyde concentration appears to be minor. This section 
considers some of the important indoor sources. 



Building Materials 

The low cost and superior bonding properties of formaldehyde 
polymers make them excellent choices as resins for the production of 
various building materials, especially plywood and particleboard. 
Resins used for building materials include urea-formaldehyde (UF) , 
phenol-formaldehyde, and melamine-formaldehyde. 

Urea-formaldehyde resin is the most common adhesive used for the 
production of indoor plywood and particleboard. It is also used in 
protective coatings and for treating paper and textiles. UF resin 
contains some free formaldehyde and decomposes and releases 
formaldehyde gas at high temperature and high humidity. 

Phenol-formaldehyde resin, which does not release formaldehyde as 
readily as UF resin, is used as adhesive for wood products requiring 
greater moisture resistance (i.e., outdoor plywood). 
Phenol-formaldehyde resin, however, is not generally used for most 
indoor wood products, because of its higher cost. 

Plywood is composed of several sheets of thin wood glued 
together. Particleboard is made by saturating small wood shavings 
with a resin (usually UF resin) and pressing the resulting mixture, 
usually at a high temperature, into the final form. Particleboard 
continuously emits formaldehyde, but at a steadily decreasing rate 
over a period of several years; in dwellings where it is used for 
furniture, partitions, etc., the emission may become large and even 
exceed the OSHA time-weighted average of 3 ppm. The emission rate 
varies as a function of several conditions, such as the original 
manufacturing process, the nature of the wood used, the quantity of 
catalyst used in curing the resin, quality control of fabrication, 



82 

porosity, humidity, cutting of the board for final use, rate of 
infiltration, and ventilation. 

The problems with plywood and particleboard are especially severe 
in mobile homes. 19 Within the last few years, there has been a 
trend to make mobile homes more airtight in an effort to conserve heat 
in the winter and minimize cooling demands in the summer. Hence, 
there is less turnover of the air in a mobile trailer, and 
formaldehyde emission from plywood and particleboard has become much 
more obvious and of increased concern. Because air-exchange rates 
affect indoor air quality, the rate of release of formaldehyde from 
these building products and the air-exchange rates in the design of 
mobile homes are especially important for the control of pollution. 



Insulation 

UP foam is used as thermal insulation in the side walls of 
existing buildings, 116 mainly single-family residential buildings. 
It is convenient and inexpensive to inject the foam through small 
holes that can be sealed after insulation is completed. 

Installation involves mixing partially polymerized UF resin with a 
surfactant (foaming agent) and an acid catalyst under pressure that 
forces air into the mixture to create a foam. The foam hardens within 
minutes and cures and dries completely within a few days. Building 
codes in the United States, concerned with the fire-safety aspects of 
UF-foam insulation, rate UF foam as a combustible material. The codes 
require that, when used on the inside of buildings, the UF foam must 
be protected by a thermal barrier of fire-resistant material. In 
England and Holland, UF insulation materials are certified for use 
only in masonry cavities of buildings. 

If the foam insulation is improperly mixed, or if improperly 
formulated UF resin is used, 159 16 the insulation may release 
formaldehyde into the building. Specific factors that have been 
identified as contributors to formaldehyde release include excessive 
formaldehyde in the resin concentrate, excessive acid catalyst in the 
foaming agent (especially important) , excessive foaming agent 
(surfactant), foaming during periods of high humidity and temperature, 
foaming with cold chemicals (optimal temperature, 50-80F) , improper 
use of vapor barriers, improper use of foams (in ceilings, etc.), and 
excessive resin. 2 116 



Combustion Appliances 

Several recent studies have reported on combustion-generated 
indoor air pollutants, namely air contaminants from gas stoves and 
heating systems in residential buildings. Laboratory studies have 
shown that gas stoves emit substantial aldehyde; formaldehyde has been 
identified as the major component of the aldehydes measured (Schmidt 
and Gotz; 15 * G. Traynor, personal communication). Formaldehyde 
emission rates for a gas stove have been measured at approximately 



83 

25,000 yg/h and 15,000 yg/h for the oven and each top burner, 
respectively (Traynor, personal communication). 



Tobacco Smoke 

Tooacco smoke is a source of several chemical pollutants, 
including aldehydes (Table 5-19), that can reach high concentrations 
in the indoor environment. The smoker's exposure to the chemical 
pollutants results principally from smoke inhaled directly into the 
lungs (mainstream smoke) . The smoke that is not inhaled directly into 
the lungs enters the space surrounding the smoker (sidestream smoke) . 
It is the sidestream smoke that is the major contributor to indoor 
pollution. The inhalation of tobacco smoke involuntarily, commonly 
referred to as "passive smoking," has only recently been the subject 
of investigation. Analysis by Hobbs e_t al_. 1<46 indicated acrolein to 
be an important component of tobacco smoke. Weber 95 used a smoking 
machine in an environmental chamber and identified substantial amounts 
of acrolein. Data on formaldehyde, acetaldehyde, and acrolein in 
cigarette smoke are presented in Table 5-20. 

Harke et al^ a measured concentrations of nicotine, carbon 
monoxide, acrolein, and aldehydes (expressed as acetaldehyde) in the 
air of an unventilated room in which a series of experiments with a 
smoking machine were performed. Important concentrations of all four 
of these compounds were observed in these experiments; however, the 
number of cigarettes per unit time was unusually high. 

It has been demonstrated that the quality of smoke from Hurley 
tobacco depends on the potassium and magnesium composition of the 
leaves. 11X When potassium was applied to the soil at 224 
kg/hectare, the aldehyde content of tobacco smoke increased from 0.41 
to 0.55 mg/cigarette. At the same time, the total particulate 
material in cigarette smoke decreased. Thus, the researchers were 
faced with both harmful and beneficial effects on smoke quality and 
therefore recommended bioassays to evaluate the potential consequence 
for health. 



AGRICULTURAL AND DISINFECTANT PRODUCTS 

Commercially grown plants require fertilizers for optimal growth 
and pesticides for disease control. Both may involve the use of 
aldehydes and theoretically could contribute to the aldehyde content 
of indoor air . Urea-formaldehyde polymers represent one of several 
groups of fertilizers and are used not only to obtain a more uniform 
release rate than is possible with soluble nitrogen, but also to 
minimize the hazards of water pollution by nitrates leached out of the 
soil. 76 Fertilizers with aldehyde compounds as a source of 
slow-release nitrogen have been used on field crops, 76 
turfgrass, 1B 6 pine seedlings, 19 and geranium. 176 

Formaldehyde has been used in a wide variety of agricultural 
operations to disinfect seeds, bulbs, roots, soil, and contaminated 



84 

TABLE 5-19 
Aldehydes Identified in Tobacco Smoke 3 

Aromatic Aromatic 

Formaldehyde Benzaldehyde 

Acetaldehyde 

Glyoxylic Acid 

Propanal Cyclic 

2-Oxopropanal 

n-Butanal Furfural 

Jsobutanal 5-Hydroxymethylf urf ural 

Galactose 

Olefinic 

Acrolein 
Crotonaldehyde 



a Data from Graedel. 



TABLE 5-20 
Quantities of Some Aldehydes in Cigarette Smoke 



Amount in 
Cigarette Smoke, 



Aldehyde 


mg/cigarette 


Reference 


Acetaldehyde 


0.18-1.44 


181 


Acrolein 


0.7 


95 


Formaldehyde 


0.02-0.04 


181 



85 

equipment, such as pots, tools, storage bins, and greenhouses. 
Walker 187 described its use to disinfect wheat and barley by 
steeping in a formaldehyde solution (1 pint of formalin in 40 gal of 
water) for 5 min and then holding in a covered container for 2 h. 
Leafspot in beets is prevented by dipping in a solution of 1 pint of 
formalin in 8 gal of water. Bacterial blight in celery is combatted 
by soaking seeds for 15-30 mm in a solution of 1 pint of formalin i 
32 gal of water. Williams and Siegel 191 * found bactericidal 
concentrations of formaldehyde on the shells of eggs exposed to 
formalin at 1.2 ml/ft 3 of incubator space. Infected laboratory 
animal housing can be decontaminated with paraformaldehyde at 10 
g/m 3 heated to 232C to release formaldehyde. 136 

Glutaraldehyde in 2% alkaline solution has a germicidal spectrum 
similar to that of formaldehyde, although it is more expensive and 
less stable. 16 3 

There are at least 60 registered pesticides containing 
formaldehyde and 75 containing paraformaldehyde as active 
ingredients. At prescribed rates, they can be used on some vegetabl 
field, and ornamental crops. Formaldehyde can also be used on 
equipment used in the culture of mushrooms, potatoes, and other crop 

Formaldehyde is an effective disinfectant against bacteria, fung 
and viruses. It kills bacteria in 6-12 h in concentrations of 1:200 
and bacterial spores in 2-4 d. It is effective against tubercle 
bacilli. It is used in dilute solutions as a disinfectant and 
preservative in cosmetics (see Chapter 7) . Formaldehyde is used in 
variety of applications as a preservative and tissue fixative for 
biologic and histologic specimens and in embalming. 163 



OTHER CONSUMER PRODUCTS 

Urea-formaldehyde resin is used by the paper industry to give 
increased wet strength to various gtades of paper. Typical paper 
products treated with UF resin include grocery bags, waxed paper, 
facial tissues, napkins, paper towels, and disposable sanitary 
products. Formaldehyde polymers are used extensively in the 
manufacture of floor coverings and as carpet backing. UF resin is 
used in binders in the textile industry to improve the adherence of 
pigments, fire retardants, or other material to cloth. It is also 
used to impart stiffness, wrinkle resistance, and water repellency 1 
fabrics. 



THE MECHANISM OF ALDEHYDE GENERATION IN THE ATMOSPHERE 
THE UNPOLLUTED, NATURAL ATMOSPHERE 

There are natural precursors of formaldehyde even in the 
atmosphere that is unpolluted by man. It contains methane, CH4, at 
about 1.6 ppm and smaller amounts of various other hydrocarbons tha 
are emitted from the earth through natural processes escape of gas< 



86 

from the earth, tree and plant emission, etc. The reaction of these 
naturally occurring hydrocarbons with photochemically generated HO 
radicals is the major natural source of formaldehyde in the clean 
lower troposphere. The HO-radical is formed through a variety of 
reactions. One important reaction sequence is initiated by the 
photodissociation of ozone, 3 , at the short wavelengths present in 
sunlight: 

3 + hv(X < 3200 A) + O^D) + 2 ( 1 Z g + , 1 A g , or 3 Z g ") (1) 

The O(^-D) atom is an electronically excited species that may be 
deactivated to a normal ground-state atom, 0( P), by collisions with 
02 and N 2 in the air (Reaction 2), or it may, on encountering a 
water molecule, form HO radicals (Reaction 3): 

0(1-0) + N 2 (or 2 ) f 0( 3 P) + N 2 (or 2 ) (2) 

O^D) + H 2 + 2HO (3) 

The HO radicals react in part with hydrocarbons present in the 
atmosphere. In the case of reaction with methane, the following 
reaction sequence (somewhat abbreviated) may occur and lead to 
formaldehyde : 

HO + CH 4 + H 2 + CH 3 (4) 

CH 3 + 2 (+ N 2 or 2 ) + CH 3 2 (+ N 2 or 2 ) (5) 

CH 3 2 + NO * CH 3 + N0 2 (6) 

CH 3 2 + CH 3 2 * CH 3 + CH 3 + 2 (7) 

- CH 3 OH + HCHO + 2 (8) 

CH 3 + 2 * HCHO + H0 2 (9) 

Formaldehyde absorbs the short wavelengths of sunlight 
(X < 3700 A) and undergoes photodecomposition. It is also 
destroyed by reactions with the HO radical and other reactive 
atmospheric species. Levy used a somewhat incomplete reaction 
mechanism involving these various formaldehyde formation and decay 
processes with the rate-constant estimates then available to estimate 
the theoretical formaldehyde concentration-versus-altitude profile 
shown in Figure 5-1. A more complete reaction scheme and updated rate 
and photochemical data lead to somewhat higher formaldehyde 
concentrations than those predicted by Levy. 37 

Thus, one anticipates in theory that, in the clean atmosphere near 
ground level during the daylight hours, the formaldehyde concentration 
will be around 1.4 x 10 10 molecules/cm 3 (about 0.0006 ppm) , owing 
to the chemistry involving only the naturally occurring components of 



87 

the atmosphere. Indeed, concentrations of this magnitude are observed 
even in the remote and seemingly uncontaminated regions of the lower 
atmosphere. If one were to include formaldehyde source terms from the 
naturally occurring nonmethane hydrocarbons, a somewhat higher 
ground-level formaldehyde concentration is anticipated. 

The Mechanism of Aldehyde Generation within the Polluted Lower 
Atmosphere 

In addition to the clean-air mechanism of formaldehyde generation 
outlined briefly in the preceding section, many other reactions occur 
within the polluted troposphere that lead to the formation of 
formaldehyde and the higher aldehydes. The major sources are the 
reactions of the anthropogenic and natural nonmethane hydrocarbons 
(alkanes, alkenes, and aromatic hydrocarbons) with HO radicals and 
ozone present in the atmosphere. It will be instructive to consider 
here some examples of these important reaction mechanisms. 



The Aldehyde-Generating Reactions of the HO Radical with the Alkanes 

There is now an abundance of both di-rect experimental and 
theoretical evidence that the reactive HO radical is present in the 
sunlight-irradiated lower atmosphere; for examples, see Calvert, 35 
Wang et_al_., 188 Davis et_al_-/ 52 53 Calvert and McQuigg, 39 and 
Crutzen and Fishman. 1 * 9 These HO radicals formed within the 
atmosphere react by H-atom abstraction with all the impurity-alkane 
molecules present in the air. The rate constants for these reactions 
are very much larger for the higher-molecular-weight hydrocarbons than 
for methane, and all the reactions lead to aldehyde formation at least 
in part. As an example, consider the reactions initiated by the 
attack of HO on n_-butane, n_-C4Hio, a typical alkane impurity found 
in the urban atmosphere. Both secondary and primary H atoms may be 
abstracted in this case: 

CH 3 CH 2 CH 2 CH 3 + HO - CH 3 CH 2 CH 2 CH 2 + H 2 (10) 

- CH 3 CHCH 2 CH 3 + H 2 O (11) 

The rate of Reaction 11 is about 3.5 times that of Reaction 10 at 
25C. Even the slower of these two reactions has a rate constant 
about 200 times larger than that of HO radical with methane (Reaction 
4). To illustrate the mechanism in which the aldehydes are formed 
following Reactions 10 and 11, the sequence of reactions of the 
n_-butyl radical, 4%, product of Reaction 10 may be considered in 
Figure 5-7; the aldehyde products are highlighted by enclosing them in 
boxes. Note that, during the course of these reactions, every 
possible straight-chain aldehyde of four or fewer carbon atoms is 
formed. Some other reactions of the alkylperoxy, RO2r and alkoxy, 
RO, radicals not shown in Figure 5-7 compete with those given here, 



88 



(0,) 



(NO) 



CH 3 CH 2 CH 2 CH 2 *- CH 3 CH 2 CH 2 CH 2 2 - - CH 3 CH 2 CH 2 CH 2 0- +N0 2 



JCH 3 CH 2 CH 2 CHO 




3 CH 2 CH 2 C00 2 
| (NO) 



CH 3 CH 2 CH 2 C0 2 +N0 2 
CH 3 CH 2 CH 2 -+C0 2 



CH 3 CH 2 CHO 



+ H0 2 



(0 2 ) 
CH 2 CH 2 2 - 

| (NO) 
CH 3 CH 2 CH 2 0- +N0 2 

X 

X 

I 3 CH 2 C00 2 - 
,(NO) 




CH 3 CH 2 -+HCO 



CH 3 CH 2 C0 2 +N0 2 
CH 3 C TT ' 




,(NO) 
CH 3 CH 2 0-+N0 2 



CH 3 CHO 



X 

CH 3 CH 2 



HCHO 



HCHO 




HCHO 



FIGURE 5-7 Example of aldehyde-forming reaction sequences after 
n-butyl radical generation from n-butane in polluted troposphere; 
pathways shown by dashed arrows are much less Important than those 
shown by solid arrows. 



89 

but the aldehyde-forming reactions are expected to dominate in the 
polluted atmosphere. 

A similar set of reactions occurs following Reaction 11 in which 
HCHO, CH3CHO, CH3CH2CHO, and methyl ethyl ketone are the 
expected major products. Indeed, all the impurity-alkane molecules 
present in the polluted atmosphere are potential sources of the 
aldehydes through similar reaction sequences. For further examples 
and a consideration of the detailed reaction mechanisms of hydrocarbon 
photooxidation, see Demerjian ^t al. 55 Present evidence suggests 
that the major atmospheric loss mechanism for the alkanes involves HO 
attack on these species. If one assumes an HO-radical concentration 
for the polluted troposphere that is consistent with theory and 
experiment, about 3 x 10~ 7 ppm, then the half-life of ri-butane may 
be estimated from the sum of the known rate constants, k]_o + kiif 
to be about 10 h. 10 Other representative alkanes, such as isobutane 
and isopentane, have similar half-lives about 10 and 8 h, 
respectively. During this rather short period in which the typical 
alkane decays, the photooxidation reactions commonly lead to more 
aldehyde molecules than molecules of hydrocarbon that have reacted. 

The Aldehyde-Generating Reactions of the HO Radical with Alkenes 

The most reactive class of hydrocarbons, the alkenes, also are 
major sources of aldehydes. The HO radical is only one of the 
reactants that stimulate aldehyde formation in this case. The 
mechanism of the reactions can be illustrated with the simple alkene, 
propylene, 3^. The complete mechanism of the HO-alkene 
reactions is not entirely clear, but it now appears probable that the 
dominant primary reaction is HO addition to the carbon-carbon double 
bond of the alkene; presumably, both terminal and internal additions 
may occur with propylene: 

CH 3 CH = CH 2 + HO -> CH 3 CHCH 2 OH ( 12 ) 

OH 
-*CH 3 CHCHj 



90 

The radical product of Reaction 12 may react by the following possible 
steps: 



00- 
- CH 3 CHCH 2 OH + O 2 ->CH 3 CHCH 2 OH 

6 

CH 3 CHCH 2 QH + NO 2 
J(0 2 ) 


II 
H0 2 + CH 3 CCH 2 OH 




CH 2 OH 



+ HO, 



In a similar fashion f the radical product of Reaction 13 may form 
formaldehyde and acetaldehyde, among other products. The rate 
constants for the HO-radical reaction with the alkenes are in general 
larger than those for the alkanes. 10 For the typical HO-radical 
concentration in the sunlight-irradiated, polluted troposphere, 
[HO] a 3 x 10~ 7 ppm, and propylene, isobutene, and trans-2-butene 
have half -lives of only 1.0, 0.5, and 0.4 h, respectively. Because 
the aldehydes are major products of this rapid interaction, the 
HO-alkene reactions are expected to be major sources of aldehydes in 
the usual hydrocarbon-polluted atmosphere. 



Aldehyde Generation through the Ozone-Alkene Reactions 

As ozone builds up in a sunlight-irradiated, polluted atmosphere, 
the interaction of ozone with the impurity-alkene molecules can become 
important, and reactions between these molecules are an efficient 
source of aldehydes. In illustration, consider the attack of ozone on 
propylene. The primary reaction leads to an unstable, energy-rich 
ozonide (Reaction 14) . Both theory and experiment suggest that, in 
the atmosphere, this species will react rapidly, in part to form 
aldehydes (Reactions 15 and 16) : 



3 + CH 3 CH = CH 2 -> CH 3 



CH 3 CHO 



0-0-0 
CH CH 




CH 2 00 



HCHO 



+ CH 3 CHOO other products 



(14) 



91 



The intermediate CH 2 2 and CH 3 CH02 species formed in Reactions 
15 and 16 may fragment by a variety of reaction paths, but they may 
also lead to aldehydes through Reactions 18-21 when easily oxidized 
compounds, such as NO and SC>2, are present: 1 * 1 



CH 2 2 +NO 

CH 2 O 2 +SO 2 

CH 3 CH0 2 +NO 

CH 3 CHO 2 +SO 2 



HCHO 


+ N0 2 


HCHO 


+ S0 3 


CH 3 CHO 


+ N0 2 


CH 3 CHO 


+ S0 3 



(18) 
(19) 
(20) 
(21) 



Present evidence 117 12I * u suggests that a significant fraction 
(greater than 20%) of the gas-phase ozonolysis of the simple alkenes 
proceeds through the so-called Criegee mechanism, of which Reactions 
15 and 16 are critical parts. Again, aldehydes are among the major 
products formed. 

The half -lives of the impurities of propylene, isobutene, and 
trans-2-butene for reaction with ozone in a highly polluted 
atmosphere, where the concentration of ozone may be about 0.2 ppm, are 
3.7, 3.3, and 0.2 h, respectively. 63 90 Because aldehydes are major 
products of this system, it is evident that the ozone-alkene reactions 
may be an important source of aldehydes in the polluted atmosphere. 

In most urban areas, the total amount of aldehydes from direct 
emission (autos, refuse burning, chemical plants, power plants, etc.) 
is usually below that of the nonmethane reactive hydrocarbons. As we 
have seen, the atmospheric chemistry results in the formation of at 
least one molecule of aldehyde from each molecule of hydrocarbon 
within a relatively short period (a few hours to a few days). Thus, 
it appears that the largest share of the total aldehyde content of 
urban air is created in the atmosphere from hydrocarbon precursors and 
that control of the direct emission of hydrocarbon, as well as 
aldehydes, will be a necessary part of any newly developed strategy to 
control ambient concentrations of the aldehydes. 



ALDEHYDE REMOVAL PROCESSES OPERATIVE IN THE ENVIRONMENT 

The accumulation of aldehydes in the atmosphere is suppressed by 
several natural removal processes. Many of the chemical steps are 
seemingly well understood; other chemical and physical processes 
remain speculative. The action of sunlight on the aldehydes results 
in their decomposition. The reaction of the reactive molecular 
fragments that are present in the atmosphere HO, HO2/ 0( 3 P), and 
N0 3 may also result in chemical degradation or transformation of 
the aldehydes. These and other important natural removal processes 
are considered in this section. 



92 

THE PHOTODECOMPOSITION OF THE ALDEHYDES 

There is a substantial overlap between the ultraviolet-wavelength 
region of the light absorbed by the simple aldehydes and the solar 
spectral distribution incident on the earth's surface. This can be 
seen in Figure 5-8 for formaldehyde, acetaldehyde, and 
propionaldehyde. The rather weak absorption bands in the 
near-ultraviolet region for the aldehydes originate from a weakly 
allowed n - IT* electronic transition, which involves largely the 
promotion of an electron in a nonbonding (n) orbital on oxygen to the 
antibonding TT* orbital associated with the carbon-oxygen double bond 
in the aldehyde. 

The initial electronically excited states of the aldehydes that 
are formed in this process are short-lived, and a large fraction of 
the excited molecules undergo molecular fragmentation or rearrangement 
very quickly. In the case of formaldehyde, the decay of the excited 
molecules occurs efficiently through either of two primary processes: 

HCHO + hv - HCHO* - H + HCO (I) 

+ H 2 + CO (II) 

Many measurements of the quantum efficiencies of these 
processes i.e., the fraction of the excited molecules that decay by a 
given path have been made in recent years; for a review of this 
extensive literature, see Calvert. 37 The results derived from two 
of these studies that should be most applicable to the reactions in 
the lower atmosphere at 25C are summarized in Figures 5-9 and 5-10. 
It is apparent from these data that the quantum yield of fragmentation 
of excited formaldehyde into the reactive free-radical fragments, H 
and HCO, in process I (<|>j) increases from near zero at 3380 A to 
near 0.8 at 3000 A. Process II, forming molecular hydrogen and carbon 
monoxide, has a longer wavelength onset, and <j>n maximizes near 
3350 A. 

After process I in air at 1 atm, the radicals formed react largely 
through Reactions 22 and 23 to generate H02 radicals and carbon 
monoxide: 

H + 2 (+ N 2 or 2 ) + H0 2 (+ N 2 or 2 ) (22) 

HCO + 02 * H0 2 + CO (23) 

The photolysis of formaldehyde in air can be a major source of the 
HO 2 radical. 

If one couples the formaldehyde-absorption data, 16 the primary 
quantum-yield estimates for processes I and II (Figures 5-9 and 5-10) , 
and the actinic-flux data for various solar zenith angles, 56 the 
apparent first-order rate constants Jj and Jjj for the occurrence 
of processes I and II, respectively, in air can be calculated. These 
and the total decay constant for formaldehyde photodecomposition (Jj 
+ J) are shown in Figure 5-11; here, the rate of process I (or II) 



93 



I ' I ' I ' I ' I 




2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 

Wavelength, A 



FIGURE 5-8 Absorption spectra for (1) formaldehyde, 75C; 
(2) acetaldehyde, 25C; (3) propionaldehyde, 25C (reprinted 
with permission from Calvert and Pitts ). Curve 4, actinic 
flux received at ground level for typical atmospheric condi- 
tions during the day (reprinted with permission from Demerjian 
et al. 55 ). e = log (I /I) /[aldehyde]^, L/mol-cm. 



94 



1 - 



CH 2 +hv 



HCO(I) 




02- 



o ' 

2700 



\0 
i t l 

3000 3300 3600 

WAVELENGTH. A 



FIGURE 5-9 Wavelength dependence of primary quantum yield of process I 
in formaldehyde photolysis. Closed circles, data of Horowitz and 

Pa 1 -WOT-!- - J "" flnon r-irflaa Hnf-a r\f Mnnvt-ofl t- artf\ Wa vnaflt - 



Calvert. 



Open circles, data of Moortgat and Warneck. 



95 



CH 2 +hv 



(E) 



08- 



6- 



04- 




I I I I 
3000 3300 

WAVELENGTH, A 



3600 



FIGURE 5-10 Wavelength dependence of primary quantum yield of 
process II in formaldehyde photolysis. Closed circles, data of 
U,-T.T< t-~ * n A r Q iw Q T-t- o'>o Open circles, data of Moortgat and 



96 




I 

20 



till 
40 60 

SOLAR ZENITH ANGLE 



80 



FIGURE 5-11 Theoretical first-order decay constants for photo- 
decomposition of formaldehyde by primary processes I and II in 
lower troposphere as function of solar zenith angle; J-j-, solid 



circles] Jjp triangles; Jj + 
from Calvert. 



open circles. Reprinted 



97 

is given by R T (or R TI ) = J T (or J ZI ) [HCHO] . With a solar 
zenith angle (angle between the sun and the vertical line 
perpendicular to the earth's surface at the point of observation) of 
0, 20, or 40, the half-life of formaldehyde decay by photo- 
decomposition in the atmosphere near sea level is expected to be 3.2, 
3.4, or 4.2 h, respectively. The rates of H0 2 -radical generation 
through the occurrence of process I (R H09 = 2J.j.[HCHO]) can be 
reasonably large and may influence the timing of the chemistry that 
controls ozone formation. 

The nature of the photochemical decay paths and their quantum 
efficiencies in air are less well established for the higher aliphatic 
aldehydes, acrolein, and the aromatic aldehydes. However, present 
evidence shows that both free-radical and intramolecular primary 
processes occur; the chemical nature of these processes for the first 
few members of the aliphatic aldehyde series are as follows: 1 * 

CH 3 CHO + hy -> (CH 3 CHO)* -> CH 3 + HCO (III) 

^ 

(0 2 )\ CH 4 + CO (IV) 

\ 
products 9 



+ hy->(CH 3 CH 2 CHO)* ->C 2 H 5 +HCO (V) 

(VI) 
products? 



CH 3 CH 2 CH 2 CHO + to -* (CH 3 CH 2 CH 2 CHO)*^ n - C 3 H 7 + HCO (VII) 

"C 3 H 8 +CO (DO 

(0 2 )\ C 2 KU + CH 2 = CHOH 00 

T 

CH 3 GHO 
products 9 



Although many studies related to these processes have been made, the 
quantum efficiency of each for molecules in air at 1 atm remains 
unclear. Thus, Demer^ian t al. 5S have reviewed the present 
information on acetaldehyde primary quantum yields, and they could 
suggest only a large range of values that may apply for processes III 
and IV. From the data of Table 5-21, it can be seen that the 




98 
TABLE 5-21 

Estimated First-Order Rate Constants for Photodecoraposition of 
Acetaldehyde as Function of Solar Zenith Angle (x ) in Lower Atmosphere a 



Rate Constant, s 



-1 



x 

deg. 


Process III 
Upper Limit 


Lower Limit 


Process IV 
Upper Limit 


Lower Limit 





3. 


75 x 


io- 5 


7.22 


x 


IO- 6 


1. 


48 


x 10" 6 


3.42 


x 10~ 7 


10 


3. 


69 x 


io- 5 


7.10 


X 


ID" 6 


1. 


45 


x 10" 6 


3.34 


x 10 


20 


3. 


51 x 


io- 5 


6.65 


X 


10" 6 


1. 


32 


x 10" 6 


3.04 


x 10" 7 


30 


3. 


19 x 


io- 5 


5.90 


X 


10~ 6 


1. 


13 


x 10" 6 


2.58 


x 10 


40 


2. 


75 x 


io- 5 


4.88 


X 


10" 6 


0. 


87 


x 10" 6 


1.98 


x 10~ 7 


50 


2. 


17 x 


io- 5 


3.64 


X 


10" 6 


0. 


59 


x 10" 6 


1.32 


x 10~ 7 


60 


1. 


48 x 


io- 5 


2.28 


X 


10" 6 


0. 


31 


x 10" 6 


0.70 


x IO" 7 


70 


0. 


76 x 


io- 5 


1.02 


X 


10" 6 


0. 


11 


x 10~ 6 


0.24 


x 10" 7 


78 


0. 


29 x 


ID" 5 


0.33 


X 


10~ 6 


0. 


03 


x 10" 6 


0.06 


x 10" 7 


8b 


0. 


05 x 


io- 5 


0.05 


X 


10" 6 


0.0 


03 


x IO- 6 


0.006 


x 10" 7 



Reprinted with permission from Demerjian et al. 56 



99 

theoretical half-life of acetaldehyde from photodecomposition in the 
lower atmosphere (x = 0) is 4.9-25 h. 

Estimates of the range of photodecomposition rate constants for 
propionaldehyde and butyraldehyde decay in the lower atmosphere ( x = 
40) have been made by Demerjian et_ al_. 5 5 with the older estimates 
of actinic irradiance given by Leighton; 112 these are summarized in 
Table 5-22. Theoretical photodecomposition half-lives of these 
aldehydes in air (x = 40) are in the range of those estimated for 
the other simple aldehydes (4-9 h) . 

All the photodecomposition data on the simple aldehydes suggest 
that the photodecomposition reactions are major loss reactions and 
that these decay paths can be an important source of free radicals in 
the atmosphere. The occurrence of processes III, V, and VII in the 
lower atmosphere will always be followed by the formation of an 
alkylperoxy radical (CH 3 O 2 f C2H 5 O 2 , or -0311702) and a 
hydroperoxy radical (HO 2 ) : 

CH 3 + O 2 > CH 3 2 (5) 

C 2 H 5 + 2 + C 2 H 5 2 (24 

n-C 3 H 7 + O 2 - n-C 3 H 7 2 (25 

HCO + O2 * HO2 + CO (23 

These radicals act to initiate the chain oxidation of NO to N0 2 and 
in turn can influence the concentration of ozone reached in the 
polluted atmosphere. 



REACTIONS OF THE ALDEHYDES WITH REACTIVE INTERMEDIATES IN THE 
ATMOSPHERE 

Several of the reactive species that are present in a 
sunlight-irradiated, NO X - and hydrocarbon-polluted atmosphere react 
measurably with the aldehydes. These include HO, 0(^P), HO 2 , 
N0 3 , and 3 . Bimolecular rate constants for these reactions with 
some of the aldehydes have been determined and are summarized in Table 
5-23. Typical concentrations of the reactive intermediates in highly 
polluted air, as estimated theoretically by computer simulation (J.G. 
Calvert and W.R. Stockwell, personal communication) , and the 
approximate relative rates of attack of these species on formaldehyde 
are summarized in Table 5-24. 

The transient species whose rates of reaction with formaldehyde 
appear to be of particular importance are those for the HO and H0 2 
radicals. The reaction with NO 3 may contribute a small amount, and 
it may be the dominant loss reaction for nighttime conditions for 
which the N0 3 concentration may remain high as the N0 2 -O 3 
reaction continues to generate this species. In the case of the HO 

and N05 radicals, the reactions are those of H-atom abstraction from 



100 



TABLE 5-22 

Theoretical Estimates of First-Order Decay Constants for Propionaldehyde 
and n-Butyraldehyde in Lower Atmosphere (X = 40) a 



Process Rate Constant, s 

C 2 H 5 CHO + hv >C 2 H 5 + HCO ( V) (4.2-2.0) x 10" 5 

>C 2 H 6 + CO (VI) 1.0 x 10~ 6 

n-C 3 H 7 CHO + hv > JT C 3 H 7 + HCO (VII) (3.2-2.2) x 10" 5 

> C 3 H 8 + CO (IX) 1.0 x 10" 6 

> C 2 H 4 + CH 3 CHO (X) 1.0 x 10~ 5 

a Reprinted with permission from Demerjian et al. 



101 
TABLE 5-23 

Bimolecular Rate Constants for Reactions of Various Reactive 
Atmospheric Species with Aldehydes 

Reactive Rate Constant at 25C, 

Species Aldehyde cc-molec s Reference 

HO HCHO (1.4 + 0.35) x 10" 11 130 

(1.5 + 0.1) x 10' 11 142 

(0.65 + 0.15) x 10' 11 165 
(0.94 + 0.10) x lO" 1 ! 11 

(0.99 + 0.11) x 10' 11 169 

CH 3 CHO (1.5 + 0.38) x 10~ n 132 

(1.60 + 0.16) x 10" 11 11 

(1.6 + 0.2) x 10" 11 142 
>2.0 x 10~11 48 

C 2 H 5 CHO (2.1 + 0.1) x 10~U 142 

C 6 H 6 CHO (1.3 + 0.1) x 10" 11 142 

0( 3 P) HCHO (1.5 + 0.5) x 10"]- 3 84 



(1.5 +0.2) x ICT^ 121 

1.64 x 10~ 13 138 



(1.50 + 0.10) x 10"" 106 

(1.61 + 0.17) x 1Q~ 1J 105 

(1.9 + 0.4) x 10~ 13 44 



CHoCHO 4.3 x IQ'^ 162 

J 4.8 x 10~ 13 122 

4.5 x 10~ 13 31 

5.0 x 10' 13 50 

C 9 H,-CHO 7.0 x I0~;j- 3 162 

25 2.3 x 10' 13 30 

n-CoH 7 CHO 9.5 x 10" ?- 3 162 

- 3 7 2.5 x ID' 13 92 

iso-C 3 H 7 CHO 1.2 x 10~ 12 162 

CH 9 =CHCHO 2.7 x 10~?- 3 30 

Z 4.9 x 10" 1J 65 

CUoCH-CHCHO 0.83 x 10'^ 30 

J 1.09 x 10~ 1Z 65 

N0 3 CH 3 CHO 1.2 x 10" 15 131 

H0 2 HCHO l.OxlO' 14 172 

3 HCHO <2.1 x 10" 24 24 



102 



TABLE 5-24 

Typical Theoretical Concentrations of Reactive Intermediates 
in Sunlight- Irradiated, NO - and RH-Polluted Atmosphere, Approximate 
Rate Constants, and Relative Rate of Attack of These Species 
on Formaldehyde (25C, 1 atm) 



Approximate 
Typical Concentrations Rate Constant, Relative Rate 



Species 


molec/cc 


ppm 






cc 


.mo lee" s 


Reaction w: 


HO 


7 


.4 x 


10 6 


3 x 


10 


-7 


1. 


1 x 


ID" 11 


1 


.00 


HO 2 


4 


.9 x 


10 9 


2 x 


10 


-4 


1. 


x 


ID' 14 





.61 a 


N0 3 


2 


.5 x 


10 9 


1 x 


10 


-4 


1. 


2 x 


10 -15b 





.036 


0( 3 P) 


1 


.7 x 


10 5 


7 x 


10 


-9 


1. 


6 x 


W 13 





.00034 


3 


4 


.9 x 


10 12 


2 x 


10 


-1 


<2. 


1 x 


W 2 * 


1 


.3 x 10~ 7 



a Rate of addition; net rate is lower as result of reverse reaction. 
b Taken as equal to that for NO^ + CH 3 CHO measured by Morris and Niki. 131 



103 

formaldehyde; the CHO radical formed here will react primarily to form 
HC>2 and carbon monoxide: 

HO + HCHO + H 2 + HCO (26) 

N0 3 + HCHO -> HONO 2 + HCO (27) 

HCO + 2 + H0 2 + CO (23) 

For the HC^-radical reaction, recent studies show that the addition 
of the radical to formaldehyde, rather than H-atom abstraction, is the 
major step: l 7 l 172 

H0 2 + HCHO - (H0 2 CH 2 0) - O 2 CH 2 OH (28) 

However, the reverse of this reaction does occur with k 2 g * 1.5 
s"" 1 (25C) , and the removal of formaldehyde does not result witn 
each occurrence of Reaction 28: 

O 2 CH 2 OH - (H0 2 CH 2 O) + H0 2 + HCHO (29) 

In laboratory studies, the O 2 CH 2 OH radical has been shown to 
react either by dissociation (Reaction 29), by disproportionation with 
H02 radicals (Reaction 30), or by disproportionation with other 
O 2 CH 2 OH radicals (Reaction 31) : 

H0 2 + O 2 CH 2 OH + H0 2 CH 2 OH + O 2 (30) 

2O 2 CH 2 OH + 20CH 2 OH + 2 (31) 

The unusual, newly identified compound, H02CH 2 OH, forms formic 
acid in laboratory experiments through the overall reaction: 

HO 2 CH 2 OH + HCO 2 H + H 2 (32) 

The OCH 2 OH radical product of Reaction 31 reacts rapidly to form 
HC0 2 H: 

OCH 2 OH + 2 HCO 2 H + H0 2 (33; 

It has been estimated that the rate of HO^jCH^H generation in a 
typical, highly polluted atmosphere in which [HCHO] s 0.02 ppm and 
[HO 2 ] ~ 2 x 10 ppm will be about 0.4 ppt/min. Conceivably, 
these or related reactions account for a portion of the HCO 2 H that 
is generated in highly polluted atmospheres. 

It is instructive to compare the relative rates of removal of 
formaldehyde by the various chemical and photochemical pathways that 
have been described. In making the estimates in Table 5-25, the 
theoretical concentrations of the reactive species shown in Table 5-24 
were used. It is seen that the attack on formaldehyde by the HO 
radical and the photodecomposition of formaldehyde are the two 



104 



TABLE 5-25 

Theoretical Relative Rates of Major Chemical and Photochemical 
HCHO Removal Reactions for Highly Polluted, Sunlight-Irradiated 
(X = 0) Lower Atmosphere 

Relative Rate 
Reaction (approximate) 

HCHO + hv >H + HCO (I) 

0.57 
>H 2 + CO (II) 

HCHO + HO ^HCO + H 2 (26) 

HCHO + H0 2 ^^0 2 CH 2 OH (28,29)1 

l" >0.0082 

H0 2 + 2 CH 2 OH >H0 2 CH 2 OH + 2 (30) J 




N0 3 + HCHO ^HON0 2 + HCO (27) 0.037 



105 

dominant homogeneous pathways for formaldehyde removal in the polluted 
atmosphere. The relative rate of removal as a result of the 
reversible H0 2 -radical addition reaction and the later reaction of 
the O 2 CH 2 OH radical is shown as a lower limit, because other 
radical reactions of this species (possible with CH 3 2 , R0 2 , 
etc.) will probably act as a permanent sink as well and also compete 
with the dissociation reaction (Reaction 29). 

If the processes considered here alone describe the removal of 
formaldehyde in the lower atmosphere, then the half-life of 
formaldehyde for these conditions, typical of the highly polluted 
atmosphere, would be somewhat less than 2.6 h. Ill-defined 
heterogeneous reaction pathways involving rainout of formaldehyde and 
removal by surface water, rock, and soil must also occur and shorten 
the lifetime of formaldehyde. Thus, O.C. Zafiriou and A.M. Thompson 
(personal communication, 1979) estimated that in the vicinity of Woods 
Hole, Massachusetts, formaldehyde enters the ocean from the atmosphere 
at the rate of 6 yg/cm 2 per year. The flux of gaseous 
formaldehyde into the sea at a remote, marine site in the equatorial 
Pacific was measured by Zafiriou et^ al^. 1 9 7 at 5 yg/cm 2 per year; 
for these same conditions, the rainout and washout of formaldehyde 
amounted to about 1 pg/cm 2 per year. These various processes 
restrict the formaldehyde buildup in the atmosphere. 

The atmospheric transport of the aldehydes over long distances is 
probably not very important, because of their short lifetimes. It is 
probably less important as a source of aldehydes in remote areas than 
the local generation from transported, longer-lived precursors, such 
as the less reactive hydrocarbons. The lifetime of formaldehyde in 
aqueous media may be somewhat greater, because the hydrated form of 
formaldehyde (HOCH20H) dominates in these conditions, and it does 
not absorb sunlight appreciably. In this case, microorganisms in the 
water appear to play an important role in the degradation process, 
which may take 30-72 h under natural conditions commonly encountered. 

All available evidence at hand suggests that the removal paths for 
acetaldehyde, propionaldehyde, etc., are very similar to those 
outlined for formaldehyde. The accuracy of the data on these 
compounds does not warrant a detailed analysis now. 

The commonly observed unsaturated aldehyde, acrolein, is 
comparatively stable toward photodecomposition. ll|S In view of this, 
it has been suggested that there may be a higher persistence for 
acrolein than the other aldehydes in photochemical smog a conclusion 
of special interest, in light of the high degree of eye irritation 
attributed to acrolein. The HO attack on acrolein is expected in 
theory to be the dominant removal mechanism, although estimates of the 
rate constant for this reaction have been made only by theoretical 
methods. Acrolein and crotonaldehyde appear to be as reactive as the 
aliphatic aldehydes in photooxidation in NO x -con tain ing mixtures, 
and it is likely that their lifetimes in the atmosphere are determined 
largely by the rate of HO-radical attack. 1 * 57 

The photochemistry of benzaldehyde and the higher homologues of 
the aromatic aldehydes is marked by the relatively high photochemical 
stability of the excited states toward decomposition. In 



106 

solution-phase studies, photoreduction and electronic energy-transfer 
processes are commonly observed with these compounds. 1 * 
Benzaldehyde , 2-methylbenzaldehyde, and 3-methylbenzaldehyde show very 
low reactivity when photooxidized in dilute N0-N0 2 mixtures in air 
in smog-chamber experiments. 57 In contrast, 1-methylbenzaldehyde 
shows a high reactivity characteristic of the aliphatic aldehydes. 
Present data do not allow quantitative estimates of the half-lives of 
the aromatic aldehydes toward photodecomposition or other possible 
light-induced reactions, but they appear to be somewhat longer than 
those observed for the aliphatic aldehydes in most cases. 



REMOVAL PROCESSES IN AQUEOUS SYSTEMS 

Very little information is available on the factors that affect 
the stability of aldehydes in aqueous systems. This section addresses 
reactions that could occur in the aquatic environment with the 
carbonyl group. It should be noted that some aldehydes may have other 
functional groups that contribute to or dominate their chemistry in 
aqueous systems. 

A reaction that many aldehydes undergo in water is hydration at 
the carbonyl group (s) to produce gem-diols (gem = geminal, with both 
hydroxyl groups on the same carbon atom) : 

RCHO + H 2 - RCH(OH) 2 

The extent of hydration depends on the nature of the R group (or 
substituent) ; electron-withdrawing substituents favor a greater degree 
of hydration. 17 The degrees of hydration at equilibrium, calculated 
from the hydration-rate data of Bell and McDougall J 8 and Smith 16 " 
for formaldehyde, chloral, acrolein, and acetaldehyde are 99.9, 99.8, 
95.0, and 60.0%, respectively, at 25C. 

At a given temperature, the ratio of the nonhydrated to the 
hydrated form of an aldehyde in water is constant. Determining 
chemical and biologic transformation and transport processes of 
aldehydes can be difficult, because the hydration equilibrium will 
shift to replenish the form removed by these processes. Because the 
hydration reaction is associated with a complex kinetic expression 
that entails both kinetic and equilibrium processes, it is difficult 
to estimate the simple half-life of an aldehyde in water. 

Biotransformation is perhaps the most important process that will 
remove aldehydes from water. It has been shown that both aliphatic 
and aromatic aldehydes are biotransformed in the aquatic environment. 
In their review of formaldehyde as an environmental contaminant, 
Kitchens and co-workers lolf reported evidence that some bacteria in 
sewage sludge can use formaldehyde as a sole carbon source and that 
complete degradation can be achieved in 48-72 h if the temperatures 
and nutrient conditions are maintained. They also cited a study 
showing that microorganisms in stagnant lake water could completely 
degrade formaldehyde in 30 h at 20C under aerobic conditions and in 



107 

48 h under anaerobic conditions. That study also showed no detectable 
loss of formaldehyde when incubated in sterilized lake water for 48 h. 

Bowmer and Higgins 23 reported that acrolein introduced into 
water samples from an agricultural area had a half-life of 29 h. When 
they reduced microbiologic activity by adding thymol to the water, the 
half-life increased to 43 h. Acrolein has been reported to be 
effectively biotransformed in activated sewage sludge and in the 
biotreatment systems that process the water used by refineries. 31 * 

Keith" compared the concentration of several organic compounds 
(including four aldehydes) in an effluent from a kraft paper mill 
before and after effluent treatment by biodegradation. The treatment 
process completely removed benzaldehyde from the effluent and removed 
73, 54, and 43% of the vanillin, salicylaldehyde, and synngaldehyde, 
respectively. 

Although there is ample evidence that aldehydes are oxidizable, 
oxidation in the aquatic environment by the alkylperoxyl radical 

(R0 2 ) is very slow. The rate constant for this radical in 

1 i 
abstracting the H atom from the acyl carbon is 0.1 M A s~ , and 

Mill 127 estimated the RO2 concentration in the aquatic environment 
to be 10~9 M. Assuming that RC>2 addition to the aldehydes is not 
important in the liquid phase (although it is important in the gas 
phase) , these values indicate that the half-life of aldehydes through 
oxidation by the R02 radical will probably be several years. 
However, aldehyde reactions with hydroxyl and alkoxyl radicals and 
other oxidizing agents are much faster, and these species may account 
for additional pathways that should be included. No information is 
available to indicate that oxidation of the diol form of the aldehydes 
would occur more rapidly or to suggest what other chemical oxidation 
processes might affect the persistence of the aldehydes in the natural 
waters. 

The effect of light on aldehydes in aqueous systems is unknown. 
It is likely that aldehydes undergo photolysis in water, but probably 
at a lower rate than in the atmosphere, because light is scattered and 
diffracted in water, and color and turbidity limit the intensity and 
depth of penetration. Hydration of an aldehyde should substantially 
retard its photolysis, because hydration will completely destroy the 
carbonyl chromophore responsible for light absorption and the 
potential for photodecomposition. 



SOME IMPORTANT SECONDARY EFFECTS OF ALDEHYDES 
IN THE CHEMISTRY OF THE POLLUTED ATMOSPHERE 

INFLUENCE OF ALDEHYDES IN PHOTOCHEMICAL SMOG FORMATION 

Bufalini and Brubaker 28 showed many years ago that the 
irradiation of the simplest aldehyde, formaldehyde, in dilute 
N0-N02~air mixtures could induce the NO-to-NO2 conversion and 
ozone formation characteristic of photochemical smog. Altshuller et 
al. 5 found that the ultraviolet-irradiated aliphatic aldehydes in 
the parts-per-million range in NO- and N^-free, dilute mixtures of 



108 

the olefinic and aromatic hydrocarbons in air induced the 
photooxidation of the hydrocarbons. They expressed concern that these 
results could modify current considerations of whether control of the 
nitrogen oxides would effectively reduce photochemical air pollution. 

Using dilute NO-NC>2-aldehyde and/or -hydrocarbon mixtures in 
air, Dimitriades and Wesson 57 studied the smog-forming reactivities 
of several aldehydes formaldehyde, acetaldehyde , propionaldehyde, 
n_-butyr aldehyde, acrolein, crotonaldehyde , benzaldehyde, 
o-tolualdehyde, m-tolualdehyde, and p_-tolualdehyde. Several criteria 
were used to establish the reactivity of the aldehyde or olefin used: 
rate of N02 formation; maximal concentrations of ozone, 
peroxyacetylnitrate, peroxybenzoylnitrate, and formaldehyde; and the 
time-weighted exposures (ppm x rain) for these four products. These 
workers concluded that the aldehydes present in auto exhaust as a 
group should be classified among the reactive exhaust components. The 
specific reactivity (reactivity per part per million) of formaldehyde, 
as measured by the rate of NO-to-NC>2 conversion, was comparable with 
that of the average exhaust alkene. However, with respect to oxidant 
yield, the specific reactivity of formaldehyde was considerably lower 
than that of the average exhaust hydrocarbon. The specific reactivity 
of the higher aldehydes was in every respect comparable with that of 
the average exhaust alkene. When tested individually, benzaldehyde 
and m- and p_-tolualdehyde were unreactive, and o-tolualdehyde was 
reactive. In mixtures, benzaldehyde and presumably all the aromatic 
aldehydes manifested reactivity as precursors of the strong eye 
irritants, the peroxybenzoylnitrates. 

Dimitriades and Wesson 57 observed another important effect of 
formaldehyde: mixtures containing formaldehyde appeared to have 
higher oxidant-yield reactivity than expected from the sum of the 
individual effects observed from the specific reactivity and 
compositional data alone; the difference increased with increasing 
formaldehyde content. 

Kopczynski jet aiL. 10B found that the photooxidation of dilute 
mixtures of formaldehyde, acetaldehyde, and propionaldehyde in the 
presence of nitrogen oxides produces the same products and biologic 
effects (eye irritation and plant damage) as does the hydrocarbon 
photooxidation. Propionaldehyde was found to be the most reactive, 
with respect to highest product yields, eye irritation, and plant 
damage. These workers concluded that, inasmuch as aldehydes are both 
primary (directly emitted) and secondary (photochemically formed) 
products, their substantial reactivities are of special importance. 
They may be expected to contribute to photochemical air pollution 
problems, not only in the central city, but in the urban, suburban, 
and rural areas downwind. 

Computer modeling of the complex chemical changes expected to 
occur in simulated, sunlight-irradiated, NO-, NO2~r hydrocarbon-, 
and aldehyde-polluted atmospheres has confirmed the observed aldehyde 
effects and pointed to the specific chemistry responsible for these 
effects. 1 " 38 39 * 5S SB 7<l 103 12 139 It has shown that the 
aldehydes (formaldehyde and acetaldehyde) present initially in 
polluted air will decrease the induction period observed for ozone, 



109 

peroxyacetylnitrate, and other products formed and their final 
concentrations, which increase in simulated smog mixtures. 

Jeffries and Kamens 91 * have demonstrated this aldehyde effect in 
experiments in a large outdoor smog chamber (Figure 5-12). In matched 
experiments carried out in sunlight simultaneously in two equivalent, 
isolated portions of the chamber, nearly equivalent amounts of a 
typical pollutant composition, hydrocarbon mixture (urban mix) and 
nitrogen oxides, were injected, in only one side, additional 
acetaldehyde was added initially (about 10% of the nonmethane 
hydrocarbon) . The photochemical reactions forming ozone proceeded 
faster and significantly higher ozone concentrations developed in the 
experiment with additional added acetaldehyde. 

Pitts et^ al^ llt9 have observed a similar effect in smog-chamber 
photooxidation experiments with a surrogate mixture of hydrocarbons 
with and without added formaldehyde (Figure 5-13) . The initial rate 
of ozone formation and the final ozone concentration reached during 
the experiment both were increased greatly by the addition of small 
amounts of formaldehyde. 

The reactions that determine the influence of the aldehydes in 
these simulated smog mixtures are largely those already described: 
radical formation through photodecomposition of the aldehydes and the 
reactions of the HO radical with the aldehydes. The ozone 
concentration developed in the NO^- and RH-polluted, 
sunlight-irradiated atmosphere is related to the NO 2 -to-NO ratio, as 
a result of the following rapid reactions involving NO, NO 2 r and 
ozone: 

N0 2 + hy + NO + (34) 

+ 2 (+N 2 , 2 ) - 3 (+N 2 , 2 ) (35) 

O 3 + NO - 2 + N0 2 (36) 

For the usual conditions in these highly polluted atmosphere, one 
expects Equation 37 to hold approximately: 35 36 112 

[0 3 ] ([N0 2 ]/[NO]) (k 34 /k 36 ) (37) 

The presence of the aldehydes can provide an additional source of the 
hydroperoxy (H0 2 ) and alkylperoxy radicals (CH 3 2 , C 2 H 5 O 2 , 
RO 2 , etc.), which may pump NO to N0 2 and hence increase the ozone 
concentration through its close relation to the [N0 2 J/[NO] ratio: 

RCHO + hu R + HCO (38) 

R + 2 - R0 2 (39) 

HCO + 2 * H0 2 + CO (23) 

R0 2 + NO RO + N0 2 (40) 

H0 2 + NO + HO + NO 2 (41) 



110 



.500 



1 I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' 1 ' I ' I - 

SEPTEMBER 2<f, 1976 _ 



E 
O. 
O. 



01 

O 



O 

z 



.400 - 



.300 - 



.200 - 



.100 - 



NO 



.000 




> i . i . i , j 



^_ i .1.1,1 



_ 

5 6 7 8 9 10 11 12 13 H 15 16 17 IB 19 

HOURS. EOT 



FIGURE 5-12 Comparison of nitric oxide, nitrogen dioxide, and ozone 
profiles in urban mix with (solid lines) and without (dashed lines) 
additional added acetaldehyde (10% of initial nonmethane hydrocarbon 
concentration). Initial conditions: with added acetaldehyde, NO , 
0.325 ppm, urban mix, 2.32 ppmC; without added acetaldehyde, NO , 
0.332 ppm, urban mix* 2.45 ppmC. Reprinted with permission from 
Jeffries and Kamens. 



Ill 



I ' I 

AV NMHC = 2450ppbC 



05 



AV NO 




TIME (hours) 



FIGURE 5-13 Effect of added formaldehyde on ozone formation 
in irradiation of surrogate mixtures of hydrocarbons and 
nitrogen oxides. Reprinted with permission from Pitts ^t al. 



149 



112 

The alkoxy (RO) and hydroxyl radicals formed in Reactions 40 and 41 
can regenerate HC>2 and RO 2 radicals in further reactions with the 
impurity aldehydes, as well as the hydrocarbons present: 



HO + HCHO 


* H 2 + HCO 


HCO + 2 


->. H0 2 + CO 


HO + RCHO 


+ RCO + H20 


RCO + 02 


- RCO0 2 


RC00 2 + NO 


-. RC0 2 + N0 2 


RC02 


* R + C0 2 


R + 2 


* R02 



(26) 
(23) 
(42) 
(43) 
(44) 
(45) 
(39) 



Obviously, the aldehydes provide a new route for a chain reaction 
driving NO to N02 in these systems, and hence they can influence the 
generation of ozone in photochemical smog. It is clear that the 
control of aldehyde emission, as well as hydrocarbon emission, is 
important in the strategy for ozone control. 



THE INFLUENCE OF ALDEHYDES ON THE FORMATION OF PEROXYACYLNITRATES IN 
THE POLLUTED ATMOSPHERE 

The aliphatic and aromatic aldehydes are important precursors of 
the notorious peroxyacylnitrates and peroxybenzoylnitrates. For 
example, all the experimental evidence and theoretical considerations 
support the view that acetaldehyde is a direct precursor of 
peroxyacetylnitrate (PAN) in the real atmosphere: 55 

CH 3 CHO + HO -f CH 3 CO + H 2 O (46) 

CH 3 CO + 2 -> CH 3 C00 2 (47) 

CH3C002 + N02 - CH3COO 2 NO2 (PAN) (48) 

NO -- CH3C0 2 + N0 2 (49) 



Similar reactions presumably lead to the formation of the higher 
homologues of PAN in the case of the higher aliphatic aldehydes 
(propionaldehyde, etc.) 68 and the aromatic aldehydes (benzaldehyde, 
etc.). 85 (Gay et_ ajL_. 68 cited references to the earlier studies 
of the peroxyacylnitrates.) The simplest member of the aldehyde 
family, formaldehyde, does not form the analogous peroxyformylnitrate, 
HC00 2 N0 2 , in substantial amounts; presumably, this is a 
consequence of the unique disproportionate of the HCO radical with 



113 

2 , which dominates the association reaction (Reaction 50) in this 
case: 

HCO + 2 - HO 2 + CO (23) 

HCO + 2 (+N 2 or 2 ) - HCOO 2 (+N 2 or 2 ) (50) 

However, in the photooxidation of formaldehyde in N0 2 -containing 
mixtures, the less stable peroxynitric acid, H0 2 NO 2 , results from 
the H0 2 reaction with N0 2 : 7e 1 " 



H0 2 +N0 2 ^H0 2 N0 2 (51) 

We may conclude that the presence of the aldehydes or their 
precursors (hydrocarbons) in the polluted atmosphere is directly 
involved in the formation of the important class of highly oxidizing, 
eye-irritating secondary pollutants, the peroxyacylnitrates and the 
peroxybenzoylnitrates . 



THE POTENTIAL ROLE OF FORMALDEHYDE IN THE ORIGIN OF FORMIC ACID IN THE 
POLLUTED ATMOSPHERE 

The gas-phase photooxidation of formaldehyde at low concentrations 
in air has been shown to lead to the products H 2 O 2 , CO, CO 2 , 
H 2 , and HC0 2 H. 28 89 l * llt7 Recently, H0 2 CH 2 OH has been 
identified as an intermediate product of this system, l72 and its 
reaction to form formic acid was noted. The kinetic results suggest 
that the reaction of H02 addition to formaldehyde leads to this new 
product. Other recent experiments with C 2 H^ , 0^ , and 
formaldehyde mixtures at parts-per-million concentrations in air 
showed that the reactive CH 2 O2 intermediate product from the 
C 2 H 4~3 reaction may lead to formic acid as well. 170 In this 
case, an unidentified intermediate is formed first by 
CH 2 02~formaldehyde reaction; this leads to formic acid anhydride 
and hence to formic acid; a possible reaction scheme consistent with 
the kinetics is the following: 

C 2 H 2 + 3 * CH 2 O 2 + HCHO (52) 

0-0 
CH 2 2 +HCHO->CH 2 OOCH 2 O- CH 2 CH 2 - (53) 

x o x 

OCH 2 OCH 2 O - HOCH 2 OCHO 

O 

(I II 
HOCH 2 OCHO -> H 2 + HCOCH (54) 



114 



HCOCH + H 2 O(aerosol) -> 2HCO 2 H (55) 

These newly discovered reaction routes to formic acid may explain, 
at least in part, the large amount of formic acid identified in aged, 
highly polluted atmospheres. 178 Conceivably, the apparent 
correlation of formaldehyde content of smog mixtures with eye 
irritation 3 85 195 is related in part to the HC02H formation, which 
would follow roughly the formaldehyde concentration in these systems 
through the reactions outlined. 

THE POTENTIAL ROLE OF FORMALDEHYDE IN THE GENERATION OF 

BIS (CHLOROMETHYL) ETHER IN HYDROGEN CHLORIDE-FORMALDEHYDE-POLLUTED 

ATMOSPHERES 

It has been observed that bis (chloromethyl) ether (BCME) is formed 
from moist air containing formaldehyde and hydrogen chloride gases. 63 
98 157 T h e overall reaction is: 

2HC1 + 2HCHO ^ C1CH 2 OCH 2 Cl + H 2 (56) 



Studies by Drew et, al. , 59 Laskin et al. x l and Kuschner et al. 1 9 
have shown that the chloromethyl ethers are respiratory tract 
carcinogens, and epidemiologic studies have indicated that they are 
human carcinogens. 1 In a recent study, 157 it was demonstrated that 
Reaction 56 occurred under dynamic conditions at room temperature with 
relatively high formaldehyde and HC1 concentrations in the gas 
phase about 1,000 and 6,500 ppm, respectively. Chronic exposure of 
rats to dilute HCl-formaldehyde-chloromethyl ether mixtures 
bis (chloromethyl) ether at about 2.8 ppb, HC1 at 10.7 ppm, and 
formaldehyde at 14.6 ppm caused a markedly increased incidence of 
squamous metaplasia of the nasal cavity and squamous cell carcinoma of 
the nasal epithelium after 136-390 d. 

From the very limited data at hand, it is impossible to extrapolate 
with great confidence to the lower, more representative concentrations 
of bis {chloromethyl) ether that would be formed with the HC1 and 
formaldehyde concentrations commonly encountered in the atmosphere. 
However, we can derive present "best" estimates from both experimental 
and theoretical data on the HCHO-HC1-C1CH20CH2C1 system. The 
reaction kinetics of the chloromethyl ether formation has not been 

determined. But, for a worst-case estimate, we may assume that an 
equilibrium concentration of the ether is formed in the atmosphere; 
this will overestimate the actual concentrations somewhat. We may make 
the reasonable assumption that equilibrium was achieved at the longest 
reaction times used in the experiments of Sellakumar e^^l- 157 and 
Frankel et^al^ 63 These data give: K^g 

*600 300 atirT 2 , where K 56 = (P^Q) (PBCME>/ 0?HC1> 2 < P HCHO> 2 ' 
and PBCME i s tJ:ie pressure of the bis (chloromethyl) ether. 



115 

A rough check may be made on the reasonableness of the 1(5 g 
estimate derived from the experiments. We may use the estimated 
enthalpy and entropy changes for Reaction 56 , AH56 and AS 5g, 
to derive a theoretical estimate of K^gt K^g = 
e ^/R e -AH/RT > Benson's 2 approximate thermochemical 
methods may be used to derive the unknown thermodynamic quantities for 
the bis (chloromethyl) ether: AH f a -58.4 3 kcal/mol, S 
86.4 2 cal mol" 1 deg" 1 (25C, 1 atm) . Coupling these 
quantities with the measured experimental enthalpies of formation and 
absolute entropies of the other reactants and products, we calculate 
the theoretical range of values, which should include K5g: 6,580 > 
K56 > 0.036 atm~2. As one anticipates if the approach in 
estimating Kgg is reasonable, the experimental value is within this 
range. Thus, one might use these data to obtain reasonable, 
order-of-magnitude results for the concentrations of bis (chloromethyl) 
ether in polluted atmospheres. 

We have used the maximal concentrations of formaldehyde observed 
in the urban atmosphere (about 0.10 ppm) and a seemingly reasonable 
maximum for hydrogen chloride (about 10 ppb) in air at 50% relative 
humidity at 25C.* Using the upper limit estimated for K5g, 6,580 
atm"~2, we estimate the maximal equilibrium concentration of 
bis (chloromethyl) ether for these conditions at about 4 x 10" 1 " 
ppb. Thus, we may conclude tentatively that there is probably little 
impact on human health from the generation of bis (chloromethyl) ether 
from formaldehyde and HC1 in the urban atmosphere. 
We must be cognizant of the potential hazard under conditions more 
favorable to bis (chloromethyl) ether formation. Thus, in principle, 
this compound could be formed in HCl-rich plumes from the incineration 
of polyvinyl chloride or other HCl-producing processes in which 
formaldehyde may be present at a high concentration. The potential 
for bis (chloromethyl) ether generation exists if fairly concentrated 
HC1 solutions are brought into contact with formaldehyde-containing 
particleboard or other formaldehyde-copolymer materials. Such 
polymers may contain free formaldehyde or they may hydrolyze to form 
formaldehyde and then interact with HC1 to lead to C1CH20CH2C1. 
There is no evidence of which the Committee is aware that allows an 
evaluation of these potential problems. 

Further direct tests for bis (chloromethyl) ether in the ambient 
air and water and new and more precise measurements of K$$ and the 
rate-determining reactions that control its rates of formation and 
decay are required, in order to evaluate quantitatively the potential 
extent of human exposure to and the influence of bis (chloromethyl) 
ether. 



*This estimate of HC1 concentration is about 10 times the number 
estimated theoretically for the "clean" lower troposphere by the 
Livermore Kinetic-Transport Model, from which [HC1] =0.9 ppb (D.J. 
Wuebbles, personal communication, 1979). It is also somewhat greater 
than the highest concentrations observed in ambient air near the 
ground. 61 69 9G 97 



116 
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Proc. Am. Assoc. Cancer Res. 21:106, 1980. 

158. Shackleford, W. M. , and L. H. Keith. Frequency of Organic 
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Environmental Protection Agency, Office of Research and 
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159. Sheldrick, J. E., and T. R. Steadman. Product/Industry Profile 
and Related Analysis on Formaldehyde and Formaldehyde-Containing 
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Formaldehyde. Columbus, Ohio: Batttelle Columbus Division, for 
U.S. Consumer Product Safety Commission, 1979. [24] pp. 

160. Sheldrick, J. E., and T. R. Steadman. Product/Industry Profile 
and Related Analysis on Formaldehyde and Formaldehyde-Containing 
Consumer Products. Part III. Consumer Products Containing 
Formaldehyde. Columbus, Ohio: Battelle Columbus Division, for 
U.S. Consumer Product Safety Commission, 1979. [39] pp. 

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Cincinnati: U.S. Department of Health, Education, and Welfare, 
Public Health Service, Consumer Protection and Environmental 
Health Service, Environmental Control Administration, 1968. 18 
pp. 

162. Singleton, D. L., R. S. Irwin, and R. J. Cvetanovic. Arrhenius 
parameters for the reactions of 0( 3 P) atoms with several 
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163. Smith, C. R. , and E. H. Spaulding. Myobactericidal agents, p. 
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Basis of Therapeutics. 4th ed. New York: Macmillan Publishing 
Co., Inc., 1970. 



129 

1.64. Smith, C. W. , Ed. Acrolein. New York: John Wiley & Sons, Inc., 
1962. 273 pp. 

165. Smith, R. H. Rate constants and activation energy for the 
gaseous reaction between hydroxyl and formaldehyde. Int. J. 
Chem. Kinet. 10:519-527, 1978. 

166. Springer, K. J., and R. C. Stahman. Diesel Car 

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1977. 32 pp. 

167. SRI International. Class Study Report. Aldehydes. Menlo Park, 
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168. Stahl, Q. R. Preliminary Air Pollution Survey of Aldehydes. A 
Literature Review. National Air Pollution Control 
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170. Su, F., J. G. Calvert, and J. H. Shaw. An FT IR spectroscopic 
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172. Su, F., J. G. Calvert, J. H. Shaw, H. Niki, p. D. Maker, C. M. 
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173. Suta, B. E. Population Exposures to Atmospheric Formaldehyde 
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[32] pp. 

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130 

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3 / 3 PP 

88 ' 



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i, . --. J. Satish, M. Meier, and H. Sommer 
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Amsterdam: Elsevier, 1976. 



131 

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341-344, 1980. 



CHAPTER 6 
ANALYTICAL METHODS FOR THE DETERMINATION OF ALDEHYDES 



Air-quality standards and pollution-control legislation are 
generally based on the assumption that exceeding some concentration of 
any given pollutant will have harmful effects on human health that 
outweigh any economic disadvantage of imposing regulatory standards. 
Accurate determination of such "threshold concentrations" demands 
accurate methods of analysis. 

This chapter discusses analytical methods currently used for 
aldehydes, including techniques of sampling and calibration, and other 
available or potentially available methods. In general, the 
analytical methods for aldehydes are difficult, and much developmental 
work is needed. Where possible, estimates of the accuracy, precision, 
and applicability of the various measurement methods are presented. 
An assessment of the state of the art is given in Chapter 2, and some 
recommendations for future action are presented in Chapter 3. 



METHODS OF GENERATING STANDARDS 

All methods of analysis have in common the need for calibration. 
Calibration is performed by applying the chosen method of analysis to 
a standard. The standard can be prepared by weighing (a primary 
standard) or measured by an independent primary reference method of 
analysis (a secondary standard). In the case of aldehydes, the 
standard is usually a liquid solution or a gas-phase mixture of one or 
more aldehydes. Liquid solutions are static; gas-phase mixtures can 
be static or dynamic (i.e., generated continuously). This section 
discusses the preparation of standards and their application to 
calibration. 



STATIC METHODS 

Aqueous solutions of aldehydes can be used as standards for 
calibration. The solutions are usually obtained by dissolving an 
appropriate amount of the desired aldehyde in water. Ordinary 
reagent-grade aldehydes are often used without purification, although 
for accurate work it is imperative to distill the aldehyde before use, 
because oxidation and polymerization occur on standing. 

132 



133 

Primary standardization can be achieved by straightforward 
application of gravimetric or volumetric methods. It is also possifc 
to prepare a secondary-standard solution of aldehyde by oxidative 
titration. Two methods described by Walker 142 are suited to the 
analysis of aldehydes other than formaldehyde: the alkaline peroxid 
and iodometric methods, which rely on the oxidation of an aldehyde t 
its corresponding carboxylic acid. Once oxidized, the acidic soluti 
can be titrated. These reactions are characteristic of all aldehyde 
so there should be no problems in applying the methods to the 
preparation of a secondary-standard solution of any (pure) aldehyde. 

It is difficult to prepare a primary-standard solution of 
formaldehyde, because pure formaldehyde is not readily available. 
There are, however, two ways to prepare formaldehyde solutions for 
standardization by a primary reference method. The easier (but less 
desirable) is to dilute commercial formalin (37% formaldehyde w/w) t 
the approximate desired concentration. Unfortunately, solutions so 
obtained will contain methanol, which is added to formalin as a 
stabilizer, as an impurity. A methanol-free formaldehyde solution c. 
be obtained by refluxing an appropriate amount of pure 
par a formaldehyde in water and filtering the resulting solution. 

For standardizing formaldehyde solutions prepared by these 
methods, Walker 11 * 2 described several methods. A simple and accurate 
primary reference method involves the addition of an aliquot of 
formaldehyde solution to a neutral solution of sodium sulfite to for 
a bisulfite addition product and sodium hydroxide. The hydroxide 
released can be neutralized with a primary acid standard to 
standardize the solution. The neutralization can be monitored with , 
pH meter. 

A second method is the bisulf ite-iodine titration procedure. 10 l 
Excess sodium bisulfite is added to the formaldehyde solution to fori 
a bisulf ite-formaldehyde adduct at neutral pH. The unreacted 
bisulfite is then destroyed with iodine. Addition of a carbonate 
buffer releases the bisulfite from the bisulf ite-formaldehyde adduct 
and the freed bisulfite is titrated with iodine (starch is used an ai 
indicator). The iodine solution itself must be standardized with 
sodium thiosulfate. Furthermore, one may encounter problems 
associated with the stability of the iodine reagent. In summary, th< 
method is complex and has several sources of possible error. 

Standardization methods based on bisulfite are recommended for us 
only with formaldehyde, because the formation of the 
bisulfite-aldehyde adduct with other aldehydes may be less than 
quantitative. llt2 



DYNAMIC METHODS 

Aldehydes are reactive compounds, so it is difficult to make 
calibration gases that are stable for any useful period. This 
precludes the use of gas-tank standards, unless the concentration of 
aldehyde is very high (several percent) . Recent advances in render ir 
gas-tank surfaces inert may alter this situation, but no data are 



134 

available. For most applications, it is currently necessary to use 
dynamic methods to generate gas-phase-aldehyde standards. 

Permeation tubes have been used to generate dynamic gas standards 
for many different types of compounds and can be used for aldehydes as 
well. These tubes contain pure compound in a length of Teflon tubing 
capped at both ends. Over time, material diffuses through the Teflon 
wall at a low and constant rate, provided that the temperature is held 
constant. 119 Tubes for acetaldehyde, propionaldehyde, and 
benzaldehyde are commercially available, and tubes could undoubtedly 
be constructed for other aldehydes. These tubes are calibrated 
gravimetrically (and are thus classified as primary reference 
standards) and can be used with a constant-flow system to generate 
primary gas standards in the concentration range of parts per billion 
to parts per million. 

Permeation tubes containing pure formaldehyde do not exist. The 
vapor pressure of pure formaldehyde would be too high to permit the 
construction of permeation tubes, if it were not already prone to 
polymerization at room temperature. Construction of a permeation tube 
for formaldehyde has been attempted with paraformaldehyde. At 80 C, 
the decomposition rate of the polymer is great enough that a usable 
permeation rate can be obtained. However, the gas in equilibrium with 
paraformaldehyde is not pure formaldehyde; it contains substantial 
amounts of methylal, methyl formate, orthoformate, and water. l< * 2 
Thus, co-emission of these gases with formaldehyde from the 
paraformaldehyde permeation tube may make gravimetric calibration 
impossible. 

One of the simplest methods for generating a gaseous aldehyde is 
to use the headspace vapor of an aqueous solution of the aldehyde. 
This method has been used to generate acrolein for use in assessing 
molecular sieves as aldehyde adsorbents. 1 * 8 The method is especially 
applicable to the generation of gaseous formaldehyde standards. It 
must be noted that, because formaldehyde is almost entirely hydrated 
to methylene glycol, CH2(OH) 2 , in aqueous solution, it has a much 
lower vapor pressure than would otherwise be expected. The apparent 
Henry's law constant (2.77 torr/mol-fraction) for formaldehyde was 
determined in 1925 by Ledbury and Blair. 76 

Use of aqueous headspace vapor does not provide a primary standard 
lirectly. The gas must be standardized in a secondary manner usually 
>y measuring the amount of aldehyde lost from the solution. It is 
>ossible to assess the efficiency of a collection device by comparing 
.he amount lost from a source solution with the amount of aldehyde 
rapped . 

A second, related method for generating gas-phase aldehyde 
tandards involves the slow addition of a dilute aqueous solution of 
n aldehyde to a gas stream in such a way that the aldehyde solution 
vaporates entirely. By knowing the rate at which the aldehyde is 
eing added to the gas stream and the flow rate of the dilution gas, 
ne can determine the aldehyde concentration in the gas stream. A 
evice implementing this method was constructed with a syringe pump to 
nject the aldehyde solutions into a heated section of tubing through 
hich the dilution gas was flowing. 77 * The purity of the gas 



135 

standards generated by this method depends on the purity of the liq 
solutions. In the case of formaldehyde, again/ it is desirable to 
methanol-free formaldehyde solutions. Gases made this way will cont 
a great deal of water (as occurs with the headspace technique) , whi 
is undesirable in some cases. There may also be some decomposition 
aldehyde. 77 As a secondary reference method, the technique must be 
used with caution. 

A promising, although relatively unused, technique that has bee 
used to generate low concentrations of aldehydes involves the therm 
or catalytic decomposition of precursor compounds. In one study, 
formaldehyde was generated through the decomposition of a gas strea 
of ^-trioxane (the cyclic trimer of formaldehyde) as it passed over 
phosphoric acid-coated substrate (A. Gold, personal communication) . 
In a second study, olefinic alcohols were thermally decomposed into 
mixture of an aldehyde and an olefin (e.g., 3-methyl-3-butene-l-ol 
gives formaldehyde, 4-pentene-2-ol gives acetaldehyde, and 5-methyl 
l,5-hexadiene-3-ol gives acrolein) . The olefinic alcohol was 
introduced into the gas phase with a diffusion or permeation tube ai 
is decomposed in a heated gold tube. Decomposition of the parent 
olefinic alcohol is virtually quantitative, so the technique general 
a primary standard. It is also possible to use gas chroma tog raphy c 
a secondary reference method to analyze for the olefin produced in 1 
reaction. When this method is used to generate standards for gas- 
chromatographic analytic techniques, the olefin can be used as an 
internal standard. One advantage of this method is that undesirable 
compounds are never handled in bulk, inasmuch as they are generated 
only in small amounts as they are used. This method has been used t 
generate standards of formaldehyde, acetaldehyde, and acrolein as Ic 
as a few parts per million. 136 Other thermal decompositions of 
precursor compounds have been used to obtain vinyl chloride and 
acrylonitrile. <t3 



SAMPLING 

An essential aspect of any analytic technique is the method of 
sampling. Choice of a method of sampling must be consistent with th 
information desired. Techniques that take an integrated sample over 
long period can concentrate pollutants and simplify analysis. Such 
techniques are applicable when the determination of mean exposure is 
desired. Techniques that provide real-time measurements usually 
require sophisticated equipment, but may be required when it is 
desirable to observe concentration fluctuation during a short period 
In the monitoring of compliance of pollutant concentrations with 
specific values set by a government agency, high precision is needed 
in the study of trends, it is more important to have a reproducible 
method. 



136 

IR 

In the analysis of air pollutants, both direct and indirect 
ampling methods may be used. The direct method uses such instruments 
s infrared and microwave spectrophotometers, which are capable of 
easuring the concentrations of compounds in situ. Direct sampling 
echniques and direct investigative methods are discussed later in 
his chapter. When the compounds of interest are present in extremely 
ow concentrations, thus precluding direct measurement, or when 
ampling sites are inaccessible to sophisticated instruments, indirect 
ampling techniques are commonly used. 

Indirect sampling can consist merely of taking a representative 
rab sample. Air to be sampled is admitted into a previously 
vacuated vessel or pumped into a deflated bag. Inert materials such 
s Teflon, Tedlar, and stainless steel are used to construct 
rab-sampling containers. The sample is returned to a central 
aboratory and analyzed as though the measurement were being made in 
itu. 

Grab sampling suffers from two defects. Because no 
reconcentration has been effected, the laboratory measurement 
echnique must be sensitive enough to determine ambient concentrations 
irectly. A more serious problem arises from the relatively long time 
hat the low concentrations of the pollutants to be measured are in 
ontact with the high surface area of the grab-sampling container, 
onspecific site adsorption occurs often, and a substantial fraction 
f the sample is lost. The container may develop a "memory 11 and give 
ise to spuriously high determinations on successive samples. Careful 
alibration and scrupulous analytic technique may minimize this latter 
efect. 31 98 122 1! 6 



reconcentration Sampling with Subsequent Analysis 

A common indirect sampling technique involves preconcentrating the 
ample at the sampling site, e.g., by passing air through an absorbing 
Lquid. There are two advantages. Preconcentration makes analysis in 
laboratory easier, inasmuch as a higher detectability limit can be 
Dlerated. And preconcentration often stabilizes the sample. In 
arapling for aldehydes, preconcentration techniques are almost always 
5ed. 

As noted previously, preconcentration devices are generally used 
i sampling aldehydes in ambient air. Impingers are used most often 
:>r trapping low-molecular-weight aldehydes. Many types of impingers 

accommodate Different sampling applications 



If the collection efficiency of the trapping solution is less than 
10%, it is desirable to use more than one impinger in series. A 
Apical arrangement for the sampling of formaldehyde (as recommended 
' NIOSH) us consists of two midget impingers in series, each 
xitaining 10 ml of water. The sample is collected at a flow rate of 1 



137 



1I 

a 



L.J 




D 



a. Midget Impinger. 
Ace Glass Co. 



b. Midget Gas Bubbler 
(coarse frit) . 
Ace Glass Co. 




c. Nitrogen Dioxide Gas Bub 
Ace Glass Co. 




J*- 



m 

1 
i 



Spiral Type Absorber. 

American Society for Testing Materials. 
Tentative Methods of Sampling Atmos- 
pheres for Analysis of Gases and Vapors, 
Philadelphia, PA, July 24, 1956. 



Packed Glass -Bead Column. 
American Society for Testing Material! 
Tentative Methods of Sampling Atmos- 
pheres for Analysis of Gases and Vapo] 
Philadelphia, PA, July 24, 1956. 




f. Midget Impinger 

Lawrence Berkeley Laboratory. 



Bubbler Absorber with D iff user. 
American Society for Testing Materials 
Tentative Methods of Sampling Atmos- 
pheres for Analysis of Gases and Vapors 
Philadelphia, PA, July 24, 1956. 



FIGURE 6-1 Various types of impingers used to sample air. a-e and g 
reprinted with permission from Pagnotto; 98 f from C. D. Hollowell 
(personal communication). 



138 

standard liter per minute (slpm) . The final solution is analyzed 
color imetrically. 

It is desirable to use an ice bath or a refrigerated sampler with 
impingers. Otherwise, low relative humidity or high ambient 
temperature may cause the impinger solution to evaporate, thus 
limiting the sampling time. The solubility and stability of the 
aldehyde in the trapping solution may also be adversely affected if 
impingers are not kept cold. 

Figure 6-2 shows two designs for aldehyde samplers used by R.R. 
Miksch e_t al. (unpublished manuscript) . The impinger sampling trains 
are contained in a small refrigerator. One sampler has a separate 
flow-control system that can sample air at a constant mass flow rate 
even when the pressure drop across the sampling train varies. The 
second sampler uses a critical orifice for flow control. 

The absorbing solution used in the impinger depends on the 
aldehyde to be analyzed. In many cases, the solution contains a 
trapping reagent that is a constituent of the analytical procedure, 
thus simplifying operations. In general, there are two categories of 
trapping solutions for aldehydes. The first "category" is simply 
water. Formaldehyde reacts rapidly with water to form the relatively 
nonvolatile hydrate, methylene glycol. Methylene glycol does have a 
finite vapor pressure, however, and saturation may occur if sampling 
times are excessively long. This problem can be minimized by using two 
impingers in series. The collection efficiency of a single impinger 
containing water will decrease with time, but two impingers in series 
will maintain a collection efficiency of over than 95% for sampling 
times of over 48 h (Miksch ^t all. , unpublished manuscript). 

Water does not appear to be an especially good reagent for 
trapping higher-molecular-weight aldehydes, because the equilibria do 
not favor the formation of the hydrates. 16 To use aqueous bubblers 
to trap higher-molecular-weight aldehydes, an additional carbonyl 
scavenger must be present in the trapping solution. Carbonyl 
scavenger compounds constitute the second category of aldehyde- 
trapping solutions. The scavengers are chosen for their ability to 
react rapidly and quantitatively with carbonyl-containing compounds to 
form nonvolatile adducts. The reagents selected have included 
bisulfite, hydroxylamine , semicarbazone , and several phenylhydrazines, 
all of which have been shown to react extremely rapidly with 
aldehydes. 17 Table 6-1 shows the collection efficiency for 
different aldehydes of various trapping solutions that contain 
scavengers. The data are compiled from a number of sources and not 
always consistent, owing to the different experimental conditions 
used. The choice of a carbonyl-scavenger trapping agent depends on 
the analytical method to be used. 

Higher-molecular-weight aldehydes also have been detected by means 
of solid adsorbents. The most widely used solid adsorbent is the 
porous polymer Tenax-GC, which has been used extensively to measure 
atmospheric organic compounds, including aldehydes, at low 
concentrations. In practice, the procedure is best suited for 
organics in the range Cg to Ci2- Pellizzari * 3 10H has reported 
e inding several aldehydes in ambient air with this method. 



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Sampler With Separate Flow Control 

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FIGURE 6-2 Sampling systems for sequential sampling of formaldehyde/ 
aldehydes. Reprinted with permission from R. R. Miksch. 



142 

Other solid adsorbents also have been used. Molecular sieves have 
been used to capture low-molecular-weight aldehydes by physical 
entrapment. Samples can be desorbed with water for analysis by 
gas-chromatographic or colorimetric techniques. Formaldehyde, 
acetaldehyde, and acrolein have all been detected with molecular 
sieves, but quantitative data are available only on acrolein. ** 8 The 
solid adsorbents, charcoal and silica gel, also have been 
investigated, but the results have not been promising. It has been 
difficult to effect quantitative desorption of collected aldehydes. 

It should be noted that a standard source of aldehyde gas is not 
required to estimate the collection efficiency of a given sampling 
device. Several devices can be placed in series and the fraction of 
the total sample collected in each device determined. This technique 
has been used to obtain collection efficiencies, 8 31 but the 
method is not necessarily reliable. It can be determined that a 
sampling device is unsatisfactory; in that event, the sample will be 
distributed throughout the system. However, the observation that no 
sample has gotten past the first trap does not guarantee that the 
collection has been quantitative, inasmuch as the sample may have 
decomposed or have been otherwise lost. The only reliable means for 
determining the collection efficiency of a sampling device is the use 
of a gas standard. 

A sampling device of recent development that has not been applied 
to aldehydes is the passive monitor. The monitor consists of a 
diffusion tube containing a trapping agent at one end. The device is 
inexpensive and easy to use, expediting large-scale sampling. Palmes 
e_t al. " have been instrumental in developing the theory of passive 
monitors and successfully constructing a passive monitor for nitrogen 
dioxide. 



Continuous Samplers 

As stated earlier, there are direct investigative methods for 
determining the concentrations of compounds in situ, e.g., infrared 
and microwave spectroscopy. None of these methods has been rendered 
sufficiently portable to be used in field studies. The details of 
these methods and their potential future applications are discussed 
later in this chapter. 

Several continuous analyzers based on wet chemical methods have 
been constructed. 27 fll * iso These analyzers are intended to combine 
the best elements of direct and indirect sampling. Air is sampled via 
an impinger apparatus to generate a preconcentrated sample that, 
instead of being transported to a central laboratory for analysis, is 
analyzed in the field. 

The continuous analyzer described by Yunghans and Munroe 150 and 
Cantor 27 is manufactured by Combustion Engineering Associates 
(CEA) . The instrument can use the pararosaniline method to analyze 
for formaldehyde, or it can use the Purpald method to measure total 
aldehydes. One problem with this instrument is that it is not 
thermostated. The color -development rate of pararosaniline is 



143 

temperature-sensitive (Lahmann and Jander 7 3 and Miksch et al. , 
unpublished manuscript), and this may lead to erratic results. The 
impinger absorber coil is also sensitive to temperature fluctuations, 
because the collection efficiency of the absorbing solution and the 
amount that evaporates into the air stream depend on temperature. The 
mercury reagents used with the pararosaniline procedure are toxic. 
Finally, the recommended color-development time is too short to allow 
full color development that ensures maximal sensitivity and stability. 



WATER 

Sampling of water for analysis of aldehydes entails obtaining one 
or more representative grab samples. Because industrial effluents and 
water from natural bodies of water are not homogeneous, some 
investigators prefer to collect several subsamples and combine them 
for analysis. These subsamples are usually collected at various times 
and from different locations. 

The preferred sample container is a glass jar with a Teflon-lined 
cap. Both jar and cap should be thoroughly cleaned with detergent anc 
water and rinsed well with distilled water and, if an organic solvent 
is used for extraction, with the organic solvent. The volume of 
sample collected depends on the desired detection. Usually 1-2 L is 
sufficient if the desired detection exceeds 2 ppb, and the GC/MS 
technique is used after proper sample extraction and concentration. 

If the time between collection and analysis is expected to be 
fairly long, the samples should be stored at 4C or, preferably, kept 
frozen, to prevent biologic or chemical degradation of the aldehydes. 



PLANT MATERIAL 

A literature review of the last two decades reveals many 
variations in the preparation of samples, methods of extraction, and 
analytic techniques for measuring aldehydes in plant tissue. 

Sample preparation has involved several procedures. Free-run juic 
of apple and grape have been concentrated 100 times and used for 
analysis. 1 * 1 132 Tomato fruit has been cored, quartered, and reduced 
to a slurry in a stainless-steel sampler before analysis. 107 Winter 
and Sundt 11 * 7 crushed plant tissue under nitrogen because of their 
evidence that 2-hexenal content of plant tissue varies with the oxyge 
concentration in the atmosphere at the time of crushing. Teranishi e 
aj.. 135 avoided crushing and processing and sampled aromas from fresh 
fruit directly. 

Extraction of aldehydes from plant products has been accomplished 
either with solvents or with distillation. Purified isopentane has 
been used to extract aldehydes from apple and fruit juices; after the 
extract is dried, it is washed with propylene glycol to remove 
alcohols; the remaining oil is ready for aldehyde analysis. 132 
Alternatively, steam distillation has been used to recover aldehydes: 
Major et^a]^. 85 steam-distilled fresh Ginkgo biloba leaves, collected 



144 

the distillate, and extracted it with ether. Tomato was similarly 
distilled and extracted with diethyl ether and dried over anhydrous 
sodium sulfate. Winter distilled strawberry fruit under nitrogen to 
avoid the oxidation of unsaturated fatty acids that are the precursors 
of aldehydes. 



WET-CHEMISTRY SPECTROPHOTOMETRIC ANALYSIS 

Wet-chemistry spectrophotometric methods of analysis for aldehydes 
continue to be the most popular and widely used. The sensitivity 
associated with the formation of a dye chromophore and the ease of 
measurement with readily available spectrophotometers are not easily 
matched by other techniques. Field samples can usually be easily 
generated with simple equipment. However, spectrophotometric 
techniques are subject to error. The specificity and degree of 
completion of the chroraophore-forming reaction must be considered, as 
well as the stability and standardization of reagents. In many cases, 
spectrophotometric techniques are slower than more direct measurement 
methods. 

To sample air, wet-chemistry spectrophotometric methods are often 
applied to preconcentrated samples that are generated with impingers. 
It is often overlooked that the detection limit for aldehydes in air 
depends on both the sensitivity of the analytical method and the 
degree of preconcentration . If the time or flow rate is changed in 
sampling with impingers, the detection limit can be changed 
radically. Typically, aldehydes in air are sampled for 0.5-8 h at 
flow rates of 0.5-2.0 L/min. 



FORMALDEHYDE 

To date, only spectrophotometric techniques have been applied in 
field studies of formaldehyde. Table 6-2 lists a variety of spectro- 
photometric techniques that can be used to analyze formaldehyde. The 
most widely used methods have been based on chromotropic acid, as 
tentatively recommended both in NIOSH 139 and in American Public 
Health Association Intersociety Committee. 10 Pararosaniline has 
been the next most popular reagent and may have some advantages over 
chromotropic acid. The remaining reagents have not been widely used. 
Some are inappropriate for field sampling, and others have not been 
adequately tested. 



Chromotropic Acid 

Ever since Eegriwe 97 described the use of chromotropic acid in a 
spot-test method for the detection of formaldehyde, there has been 
widespread interest in using this reagent for spectrophotometric 
determination of formaldehyde. As stated above, a tentative method 
using this reagent has been suggested by both NIOSH 139 and the 



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146 

Intersociety Committee 10 for determining formaldehyde concentration 
in occupational environments. 

The chromotropic acid method suggested by NIOSH and the 
Intersociety Committee involves the collection of samples by passage 
of air through two midget impingers in series, each of which contains 
20 ml of distilled water. When a suitable volume of air has been 
sampled (1 h of sampling at 1 slpm) , the contents of the midget 
impingers are analyzed separately. For analysis, the contents of an 
impinger are diluted quantitatively to a known volume. With 1% 
chromotropic acid, an aliquot of the sample is brought up to 0.025% 
chromotropic acid. Concentrated sulfuric acid is then added at 3 
parts acid to 2 parts sample. The heat of mixing develops the color; 
after cooling of the sample, the absorbance is read at 580 nm 
(extinction coefficient, e/ 8.9 x 10 3 ) . 

The reported sensitivity of the method is 0.1 ug/ml of 
color-developed solution, which corresponds to formaldehyde at 
approximately 0.04 ppm in the sampled air (see Table 6-2). Acrolein 
is reported to be a positive interference at few percent. Ethanol, 
higher-molecular-weight alcohols, and phenols can be negative 
interferences, but at concentrations not normally encountered in the 
atmosphere. Olefins in tenfold excess over formaldehyde can be 
negative interferences at approximately 10%. Aromatic hydrocarbons 
also constitute a negative interference. With the exception of 
olefins, the interferences listed are not likely to be encountered in 
substantial concentrations during atmospheric sampling. And even in 
the case of olefins, the interference is not serious. 129 

Early work by Altshuller et al. 8 indicated that nitrogen dioxide 
did not interfere. However, the same cannot be said for nitrite and 
nitrate. Indeed, there is a chromotropic acid assay for nitrate 
similar to the formaldehyde assay. llfl * Cares 28 was the first to 
investigate systematically the nature of the nitrite and nitrate 
interference and methods of eliminating it. She found that both 
interfered with formaldehyde analysis nitrite slightly more than 
nitrate. When they were present in tenfold molar excess, negative 
interferences of 60% and 30%, respectively were observed. Later work 
by Krug and Hirt 72 confirmed these findings. To overcome these 
interferences, Cares recommended a modified procedure that uses a 
solution of sodium bisulfite for sampling. This solution is 
neutralized and heated to reduce the oxides of nitrogen to nitric 
oxide, which outgasses from the solution. The sample is then analyzed 
as before, with chromotropic acid and sulfuric acid. This procedure 
has not been used in field studies, probably because of its complexity. 

Oxides of nitrogen can probably interfere with analysis for 
formaldehyde with chromotropic acid. There is evidence that a major 
sink for NC^ in the atmosphere involves its transformation to nitric 
acid (or its subsequent transformation to nitrate-containing aerosols) 
by way of OH attached on nitrogen dioxide. Furthermore, nitrogen 
dioxide can be converted to nitrite and nitrate in the presence of 
water or sulfuric acid, 33 integral constituents of the analytic 
method. 



147 

It is not clear that the tentatively suggested method is 
optimized. Bricker and Johnson, 25 who originally developed a 
procedure using chromotropic acid, reported that full color 
development depended on heating of the reaction mixture for 30 min. 
Later work by West and Sen 11 * 5 and Altshuller et al . 8 suggested 
that the heat generated by the mixing of concentrated sulfuric acid 
with the sample solution was sufficient to drive the color -development 
reaction to completion. This conclusion is open to question, inasmuch 
as the peak temperature and duration of heating could be affected by 
the choice of reaction vessel and by the ambient temperature. Bricker 
and Johnson 25 also reported that the sulfuric acid concentration 
should be at least 67% for maximal color development. West and 
Sen, i<tS however, reported that color development increased strongly 
with increasing sulfuric acid concentration until a value of 85% was 
reached, after which the dependence lessened. This finding was 
acknowledged by Altshuller et al. , e who went so far as to recommend 
that samples be collected with impingers containing chromotropic acid 
in concentrated sulfuric acid. Later simplex optimization work by 
Olansky and Deming 9 6 indicated that color development is maximal at 
57% and declines at higher values. 

In sum, it seems that the chromotropic acid method suffers from 
several deficiencies. It is not clear that the procedure is optimized 
for maximal sensitivity; the method suffers from interferences by a 
number of substances, some of which will undoubtedly be encountered 
during field sampling; and modifications designed to reduce these 
interferences introduce additional complexities. 



Pararosaniline 

A second reagent used for the measurement of formaldehyde 
concentrations is pararosaniline, which was first introduced in the 
form of a spot test by Schiff (1866 ). 120 In the classical Schiff 
test for aldehydes, the intense pink color of basic fuchsin is 
bleached with sulfur dioxide in basic solution. When an aldehyde is 
added to the solution, it reverses the bleaching process, and the 
basic fuchsin color returns. This spot test is neither quantitative 
nor formaldehyde-specific. 

Lyles, Dowling, and Blanchard 811 were the first to develop a 
pararosaniline technique that produced a stable color and reproducible 
results. The technique is as follows. Samples are generated by 
passing air through a midget impinger containing distilled water. A 
reagent solution containing 0.05 M tetrachloromercurate II and 0.025% 
sodium sulfite is mixed with the sample in a ratio of 1 to 10. A 
second reagent solution, prepared by dissolving 0.16 g of 
pararosaniline and 24 ml of concentrated hydrochloric acid in water 
sufficient to total 0.1 L, is added to the sample in a ratio of 1 to 
11. After 15 min, the absorbence is read at 560 nm. 

Several aspects of this analysis require comment. Lyles et al. 
took note of earlier work 95 llt3 and were careful to use pure 
pararosaniline in place of basic fuchsin reagent. The latter is often 



148 

contaminated with pararosaniline and is difficult to purify. Earlier 
problems with reagent stability and reproducibility may have resulted 
from insufficient purity. 

The use of tetrachloromercurate II follows the work of West and 
Gaeke, 1 * 3 who used pararosaniline in conjunction with formaldehyde 
to determine sulfur dioxide. West and Gaeke sampled atmospheric 
sulfur dioxide by bubbling air through a solution of sodium 
tetrachloromercurate II. The sulfur dioxide was trapped and 
stabilized as a dichlorosulf itomercurate II complex, which then 
reacted with acidic pararosaniline and formaldehyde. 

The pararosaniline method developed by Lyles et_ al_. 8 is 
substantially the same as that used by the Combustion Engineering 
Associates (CEA) 555 continuous analyzer. The latter is used by many 
industrial hygienists to determine formaldehyde in workplace 
environments. Its primary virtue is its ability to give nearly 
real-time measurements. 

Recent work has led to further refinements in the pararosaniline 
technique. Miksch et al. took note of the work of Lahmann and 
Jander, 73 German workers who investigated the dependence of the 
technique of Lyles et al. on each of the reagents used. In 
particular, the stability and sensitivity of the method could be 
markedly improved through a fivefold reduction in the sodium sulfite 
concentration. Substantial temperature effects on both stability and 
time of development of the color were also noted. 

In the same study, Miksch et al. questioned the use of 
tetrachloromercurate II. Because the original role of this reagent 
had been to stabilize the sulfur dioxide collected in the procedure of 
West and Gaeke, 11 * 3 its function during formaldehyde determinations 
was not clear. Investigation revealed that reversing the order of 
addition of the reagents permitted the hazardous mercury reagent to be 
eliminated. No metal ion at all was found to be necessary. 

The procedure developed by Miksch et^ al_. is as follows. Samples 
are collected in impingers containing deionized distilled water. The 
samples are collected, shipped back, and stored at 5C to enhance 
sample stability before analysis. In the laboratory, the contents of 
two impingers operated in series are pooled, and the solution is 
diluted to a known volume. A reagent solution, prepared by dissolving 
0.16 g of pararosaniline and 20 ml of concentrated hydrochloric acid 
in water sufficient to total 100 ml, is added to an aliquot of the 
sample in a ratio of 1 to 10. After 10 min, a second addition of 0.1% 
sodium sulfite solution is added to the sample in a ratio of 1 to 11. 
The reaction vessels are capped (to prevent outgassing of sulfur 
dioxide), and the color is allowed to develop for 1 h. The absorbance 
is then determined at 570 nm (extinction coefficient, 1.88 x 10 4 ) . 

The procedure is specific for formaldehyde. Only sulfur dioxide, 
an integral part of the procedure in the form of sulfite, constitutes 
a potential interference. This interference can be largely removed by 
basifying the impinger solutions with 1 or 2 drops of 1 N sodium 
hydroxide before analysis to destroy any formaldehyde-sulfur dioxide 
adduct. This allows ambient concentrations of sulfur dioxide up to 
500 ppb higher than normally encountered to be tolerated. Miksch et 



149 

al. nave reliably used the pararosaniline procedure in measuring 
several thousand indoor and outdoor air samples. 



Acetylacetone 

A very sensitive fluorimetric method for the determination of 
formaldehyde is based on the Hantzsch reaction between acetylacetone 
(2,4-pentanedione) , ammonia, and formaldehyde to form 
3,5-diacetyl-l,4-dihydrolutidine. The reagent was first used in a 
colorimetric procedure by Nash, 911 who also reported that the adduct 
fluoresced. Belman 1 9 developed a fluorimetric procedure based on 
this property. 

The procedure of Belman 19 is as follows: Equal volumes of 
formaldehyde solution and a reagent consisting of 2 M ammonium acetate 
and 0.02 M acetylacetone (pH, 6) are mixed and incubated at 37C for 1 
h. After cooling to room temperature, the fluorescence is determined 
(Xexcite = 41 nm ' *emit * 51 nm ) Tne standard curve is 
linear with formaldehyde from 0.005 yg/ml to about 0.4 yg/ml and 
deviates slightly from linearity from 0.4 \ig/ml to 1.0 yg/ml. 
Above 1.0 yg/ml, the formaldehyde can be determined color imetrically. 

This method has been particularly chosen by the wood industry in 
determining emission from particleboard and plywood. 20 90 Under 
controlled conditions in specially designed chambers, the formaldehyde 
content of headspace vapor over materials being examined is 
determined. This test is being considered for promulgation as a 
European standard. 113 Acetylacetone has not been used for sampling 
for formaldehyde in ambient air. In this application, possible 
interference by oxides of nitrogen, sulfur dioxide, and ozone must be 
considered. 9 



Other Methods 

It has already been mentioned that there are a fairly large number 
of spectrophotometric methods for the determination of formaldehyde, 
in addition to the two discussed above. In general, these methods 
either have not been fully evaluated or suffer from major defects. 
Several alternative wet-chemistry spectrophotometric methods of 
analysis are listed in Table 6-2. Closely analogous methods, based on 
spectrofluorometry, have also been suggested, as shown in Table 6-3. 
One final analogous method deserving serious consideration is based on 
chemiluminescence. All these methods are discussed below. 

An older reagent that has been considered as a candidate for the 
colorimetric determination of formaldehyde is phenylhydrazine. 
Reaction of this reagent with formaldehyde, followed by oxidation of 
the adduct with ferricyanide, leads to the formation of an anionic 
species absorbing at 512 nm. 88 The essential drawback encountered 
is that color is not stable and fades with time. Under some 
procedural conditions, aliphatic aldehydes interfere. 13 * Other 
possible interferences have not been investigated. 



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151 

A reagent similar to chromotropic acid in both its structure and 
its associated analytic technique is 7-amino-4-hydroxy-2- 
naphthalenesulfonic acid (J-acid). 116 The adduct formed is 
fluorescent, and a second, more sensitive, technique that takes 
advantage of this property has been developed. 118 Formaldehyde 
precursors interfere under the harsh conditions of both these 
techniques, and acrolein also interferes with the second technique. 
Other possible interferences have not been adequately investigated. 
The reagent phenyl-J-acid is a minor modification of J-acid. 116 

Two other reagents must be mentioned as potential candidates for 
the wet-chemistry determination of formaldehyde, although they have 
not been adequately tested. The reagent phenylenediamine may be 
oxidized by hydrogen peroxide to produce Bandrowski's base, 3,6-bis(4- 
aminophenylimino)cyclohexa-l,4-diene-l,4-diamine U ma x' 485 nm) . 
The reaction is catalyzed by formaldehyde 12 and may form the basis 
for an analytic procedure. At present, only sulfur dioxide in 
100-fold excess is known to interfere. The second reagent is 
tryptophan, which reacts with formaldehyde in the presence of 
concentrated sulfuric acid and iron to give a colored species. 30 
The reaction was found to be extremely sensitive and free of 
interference from a wide range of compounds, but its suitability as a 
field sampling method has not been tested. The instability of some of 
the reagents used may present a problem. 

Two final reagents have occasionally been used to assay for 
formaldehyde: 3-methyl-2-benzothiazolone hydrazone (MBTH) and 
4-amino-3-hydrazino-5-mercapto-l,2,4-triazole (Purpald) . They are 
specific only for the class of aliphatic aldehydes as a whole, and 
precautions must be taken to ensure that separate formaldehyde is the 
only aldehyde present. These reagents are discussed more fully in the 
next section. 

Several workers have attempted to develop fluorometric methods of 
analysis for the determination of formaldehyde. The better known 
examples are shown in Table 6-3. In general, the techniques are 
sensitive to the design of the instrument note the different 
sensitivities reported for the same reagent at different times. The 
later work actually shows reduced sensitivity. Problems common to 
many fluorescence techniques are susceptibility to sample matrix 
variations and nonlinear standard curves. With the exception of 
acetylacetone, none of the reagents shown has been used in reported 
studies. 

A final method deserving serious consideration is based on a 
chemiluminescent reaction of formaldehyde and gallic acid in the 
presence of alkaline peroxide. 128 In a flow system where the 
reagents can be mixed immediately before passage into an optical cell, 
formaldehyde concentrations as low as 3.0 ng/ml can be detected an 
increase in sensitivity of more than an order of magnitude relative to 
the color imetric procedures just described. A second distinct 
advantage is that the working linear range of response extends over 
five orders of magnitude. 

The chemiluminescence method may not be completely 
formaldehyde-specific. Acetaldehyde was reported to give a response 



152 

that was less than one-tenth that of formaldehyde. Other aldehydes 
were not tested. Two dicarbonyl compounds, glyoxal and methylglyoxal, 
gave a response equal in magnitude to that of formaldehyde. lze 
These compounds would not normally be encountered, except perhaps in 
biologic samples. 

Proper design of the flow system and optical cell are essential to 
the chemiluminescence method. With proper design, the apparatus can 
be inexpensive. The method is best suited to analyzing aqueous 
impinger solutions at a central laboratory or to continuous monitoring 
at selected stationary sites (C.D. Hollowell, personal communication). 



TOTAL ALIPHATIC ALDEHYDES 

Measurements of total aliphatic aldehydes are based on chemical 
reaction behavior imparted by the presence of the formyl group common 
to all aldehydes. As with formaldehyde, only wet-chemistry 
spectrophotometric techniques have been used for sampling total 
aliphatic aldehydes under field conditions. The application of more 
sophisticated instrumental techniques to the determination of total 
aliphatic aldehydes is inadvisable, because it is usually easier and 
more desirable to identify and measure each specific aldehyde 
separately. 



3-Methyl-2-benzothiazolone Hydrazone 

By far the most commonly used reagent for the determination of 
total aliphatic aldehydes is MBTH. First introduced by Sawicki e_t 
al. , 117 this reagent has been used for measuring lower-molecular- 
weight aliphatic aldehydes in auto exhaust and urban atmospheres (see 
Table 6-2) . 

A tentative method using MBTH for determining aldehydes in ambient 
air was given by the Intersociety Committee. 10 The method is as 
follows. Air to be sampled is bubbled through 0.05% aqueous MBTH 
contained in a midget impinger. After dilution to a known volume, an 
aliquot of an oxidizing reagent containing sulfamic acid and ferric 
chloride is added. After 12 min, the absorbence is read at 628 nm. 
At the recommended sampling rate of 0.5 slpm, assuming a minimal 
detectable absorbence change of 0.05 unit, a concentration of 0.03 ppm 
could be determined after sampling air for 1 h. 

The original method of Sawicki e_t al^ 117 used ferric chloride 
alone as the oxidizing reagent. Because of turbidity, acetone was 
incorporated into the dilution scheme. Hauser and Cummins 53 
effectively eliminated the turbidity by adding sulfaraic acid to the 
oxidizing reagent. The molar absorptivities of the aldehydic adducts 
formed vary between approximately 48,000 and 56,000. The formaldehyde 
adduct has a molar absorptivity of 65,000. Altshuller et al. 3 
recommended that concentrations of aldehydes determined by MBTH should 
be multiplied by a factor of 1.25 to account for the difference in 



153 

response between formaldehyde and the remaining aliphatic aldehydes. 
The recommendation has not been followed in reported uses of MBTH. 

Many classes of compounds, particularly those containing nitrogen, 
react with MBTH to give colored products. Most of these compounds are 
not encountered during atmospheric sampling. Nitrogen dioxide has 
been reported to interfere through formation of nitrite and nitrate in 
water . 



Purpald 

A reagent recently developed for the determination of aliphatic 
aldehydes is Purpald. First described by Dickinson and Jacobsen, 35 
the reagent can be used quantitatively as follows. 62 A basic 
solution of Purpald is added to aqueous samples containing 
formaldehyde. The mixture is aerated for 30 min to ensure oxidation, 
and the absorbence is determined at 549 nm. Assuming that impingers 
are used for sampling air at a rate of 1 slpm for 1 h and that the 
minimal detectable absorbence difference is 0.05 unit, a concentration 
of 0.04 ppm can be detected. Purpald suffers from the same drawback 
as MBTH: it gives different responses to different aldehydes. 
Potential interfering substances encountered in atmospheric sampling 
have not been completely examined, but no interference from a wide 
variety of test compounds was noted by the originators. 35 



Other Methods 

2,4-Dinitrophenylhydrazine (DNPH) has received considerable 
attention as a reagent for determining aldehyde concentrations. The 
vast majority of DNPH techniques attempt to separate and identify the 
individual aldehydic adducts through the use of thin-layer 
chromatography, gas chromatography, or high-performance liquid 
chromatography . Wet-chemistry spectrophotometric procedures are based 
on the formation of a chromogen absorbing at 440 nm. 100 10S These 
procedures have been hampered by the interference of ketones and 
problems with reagent stability. The minimal detectable concentration 
of aldehydes with these procedures is about 0.2 ppm. 

A method deserving mention is the bisulfite method published by 
the Los Angeles Air Pollution Control District. 7 * Air is sampled 
with impingers containing aqueous bisulfite. The aldehydes react to 
form aldehyde- bisulfite adducts. The excess bisulfite is destroyed, 
and the solution is basified to liberate the bisulfite bound in the 
adducts. The freed sulfite is titrated with iodine and starch. The 
method is cumbersome, the adducts are not stable for long periods even 
if kept on ice, and the iodine reagent is sensitive to air and light. 



154 



ACROLEIN 



Acrolein is a highly toxic aldehyde; a threshold limit value (TLV) 
of 0.1 ppm f has been established by the Occupational Health and Safety 
Administration (OSHA). 1 " This standard is 30-fold lower than the 
corresponding TLV for formaldehyde. Acrolein is the only aldehyde 
other than formaldehyde for which there is a specific wet-chemistry 
spectrophotometnc method of analysis. 



4-Hexylresorcinol 

The most popular method for determining acrolein in air uses 
4-hexylresorcinol. 31 68 139 Air is typically drawn through two 
midget impingers at 1 slpm to collect the sample. The collecting 
solution can be either 1% sodium bisulfite or a reagent containing 
4-hexylresorcinol, mercuric chloride, and trichloroacetic acid in 
ethanol. Samples collected in bisulfite are analyzed by adding 
4-hexylresorcinol and mercuric chloride in ethanol and then a solution 
of trichloroacetic acid in ethanol. The solution is heated for 15 mm 
at 60C, and the resulting color is measured at 605 nm. Samples 
collected in 4-hexylresorcinol are analyzed simply by heating and 
measuring the color. For field sampling, the simplicity of the latter 
method is offset by the hazards of handling the toxic and corrosive 
reagent. In addition, the reagent and the samples collected are not 
very stable, and samples must be analyzed within a few hours. The 
bisulfite method is somewhat more complex, but it is safer to use. 
Besides using a less hazardous collecting solution, this method 
produces samples that are stable for up to 48 h if they are kept 
refrigerated, thus permitting later analysis at a central laboratory. 

A recent paper by Hemenway et al. 5I pointed out a potential flaw 
in the 4-hexylresorcinol method given by NIOSH. 139 Apparently, the 
order of addition of reagents for analysis differs between field 
samples and calibrating solutions, and this may lead to 
underestimation by as much as 35%. The validity of this objection 
needs to be established. 



Other Methods 

A very sensitive procedure for the determination of acrolein is a 
fluorimetric method using m-aminophenol . 1 The procedure can detect 
acrolein at concentrations as low as 10 ng/ml in an aqueous test 
solution. No interference is reported for many alcohols, amines, 
ammo acids, and polyamines. Other aldehydes do not interfere unless 
they have a double bond in conjugation with the formyl group analogous 
to acrolein (e.g., crotonaldehyde) . The procedure shows promise, but 
has not been applied to environmental samples. 

Chromotropic acid has also been suggested for acrolein 
determinations. H9 In the formaldehyde procedure using Chromotropic 
acid, the response to acrolein is regarded as an interference; 



155 

however, the absorbance maximums are sufficiently different that it i 
possible to measure the two compounds separately. A method for the 
simultaneous determination of formaldehyde and acrolein in air has 
been proposed by Szelejewska. 1 3 3 Samples are collected in bisulfite 
at 1 slpm before the addition of chromotropic acid in sulfuric acid. 
After the addition of the chromotropic acid reagent, the absorbance i 
measured at both 420 and 575 nm. The two absorbances are fitted to a 
linear system of two equations that, when solved, gives the 
concentrations of the two aldehydes. This method has not been used i 
practice. 

Two other reagents for the analysis of acrolein have been 
discussed by Cohen and Altshuller . 3 l The first, phloroglucinol, 
reacts with acrolein to produce a red color. The reaction is subject 
to interference from formaldehyde and oxides of nitrogen and has not 
been used. The second, tryptophan, reacts with acrolein in acid 
solution to produce a purple color. The sensitivity of the tryptopha 
method is only one-fourth that of the 4-hexylresorcinol method. 
Furthermore, in view of the fact that a similar method has recently 
been used to determine formaldehyde, 30 the reagent may be subject to 
interference from formaldehyde. 



ACETALDEHYDE 

The only color imetric method reported to be specific for 
acetaldehyde uses diazobenzene sulfonic acid. 11 * 2 Unfortunately, no 
data are available on the sensitivity or interferences associated wi 
this method. Some efforts have been made to take advantage of the 
rather high volatility of acetaldehyde, in separating it by 
distillation from other aldehydes. Procedures that use this method 
are too cumbersome to be reliable. A method has recently been 
published for determining acetaldehyde in the presence of formaldehy 
in biologic materials. 91 * Acetylacetone reacts with the solution, 
which eliminates the formaldehyde, and then the acetaldehyde is 
analyzed with p_-phenyl phenol. This method does not take into accou 
interferences from higher aldehydes; it is not actually a procedure 
for acetaldehyde, but rather for nonformaldehyde aldehydes. The onl 
methods available for determining acetaldehyde involve the separatic 
of all the aldehydes that are present with gas or liquid 
c h r oma tog r aphy . 



OTHER ANALYTICAL METHODS 



SPECTROSCOPIC METHODS 



Microwave, infrared, and laser-fluorescence spectroscopy have aJ 
been used to measure aldehyde concentrations in ambient air directls 
Each of the methods is prohibitively expensive for ordinary field 
sampling. The instrumentation required is often cumbersome and 



156 

delicate, is seldom portable, and requires sophisticated maintenance 
and support facilities. 

Microwave rotational spectroscopy can measure low concentrations 
of many compounds in gas-phase samples. Rotational resonances are 
very sharp at microwave frequencies and low partial pressures, so 
sample spectra can be easily resolved. Formaldehyde has been 
monitored continuously at concentrations as low as 10 ppb in air with 
a two-stage membrane separator for preconcentration. s 7 Acetaldehyde 
has been detected directly at 15 ppm. 58 This is far above normal 
concentrations for ambient air, and the technique is not routinely 
applicable to ambient-air analysis. Microwave spectroscopy has also 
been used to determine acrolein, acetaldehyde, and formaldehyde in 
tobacco smoke. 66 The sensitivity of the technique was reported to 
be 2 ppm, but, again, this concentration is rather high and would not 
normally be encountered in ambient air. Furthermore, the response 
time of the instrument is long, rendering the technique insensitive to 
changes in concentrations. 

Infrared spectroscopy is promising, owing to the sharpness of the 
rotational and vibrational peaks observed for gas-phase samples. 
Unfortunately, good spectral resolution (less than 0.1 cm" ) and 
rapid measurements are hampered by the low power of infrared sources. 
To overcome this difficulty, Fourier-transform infrared (FTIR) methods 
have been developed in which conventional Fourier-transform methods 
are used to derive the absorption bands. FTIR instruments are 
commercially available, but are exceedingly expensive. In one 
application, formaldehyde was continuously monitored at ambient 
concentrations of less than 10 ppb with an FTIR system. 137 The 
system was used with a Michelson infrared interferometer with a 
sophisticated multiple-reflection optical cell whose pathlength was 2 
km. Longer pathlengths could not be obtained, because of image 
overlap. Other aldehydes were not measured. 

A fluorescence procedure based on the direct excitation of 
formaldehyde by a dye laser has been reported. 15 Formaldehyde as 
low as 50 ppb in air could be detected. The authors suggested that 
further refinements would increase the sensitivity. The application 
of this technique to other aldehydes is restricted by the weaker and 
less well-resolved absorption spectra in the accessible spectral 
region. 



CHROMATOGRAPHIC METHODS 

Three chroma tographic techniques have been applied to the analysis 
of aldehydes: gas chroma tography, liquid chroma tography, and ion 
chroma tography. Gas -chroma tographic analysis of aldehydes generally 
takes one of two forms: direct analysis by gas or solution injection 
and derivatization followed by analysis. 

Formaldehyde presents special problems with respect to direct 
analysis by injection. In a flame ionization detector (FID), a 
universal detector widely used for quantitative work, formaldehyde 
decomposes and gives a very small response. Thermal conductivity 



157 

detectors (TCDs) are less sensitive and respond only to very high 
concentrations of formaldehyde. An electron capture detector (ECD) 
has a limited linear response range and is sensitive only to 
conjugated carbonyl groups. The photoionization detector (PID) is 
reported to be sensitive to formaldehyde (HNU Company, Newton Upper 
Falls, Mass.), but appears to have some drawbacks. Specifically, a 
high-energy lamp is required to detect formaldehyde; this drastically 
reduces both the selectivity and the lifetime of the detector. 96 

In principle, it is possible to circumvent the insensitivity of 
the FID to formaldehyde by catalytically reducing formaldehyde to 
easily detectable methane. 32 Because hydrogen is required for the 
operation of the FID, the reduction is easily achieved by passing a 
mixture of the column effluent and hydrogen gas over a short bed of 
catalyst before introduction into the FID. Deposits of nickel, 
thorium, and ruthenium on fine-mesh glass beads have all been used 
successfully to reduce formaldehyde to methane. The lack of success 
in applying the technique to routine analysis of formaldehyde can be 
attributed to problems in choosing proper gas-chromatographic 
conditions. Apparently, it is difficult to pass formaldehyde through 
any of a variety of column -pack ing materials quantitatively. 26 

With the exception of formaldehyde, aldehydes may be analyzed by 
direct gas injection if concentrations are high enough. By using a 
six-port valve equipped with a 1-ml gas-sampling loop, aldehydes can 
be routinely detected with an FID at concentrations as low as 0.03 pp 
without preconcentration (Analytical Instrument Development, Inc., 
Avondale, Pa.). It is important to recall, however, that gas 
chromatography excels at separation, but provides minimal 
identification. Ambient-air samples often contain hydrocarbons, and 
their responses may overlap and obscure the aldehydic responses. 
Bellar and Sigsby 18 reported a complex automated gas chromatographic 
technique to analyze for C 2 -C 5 aldehydes that avoided this 
problem. Hydrocarbons and aldehydes from an air sample flowed onto 
polar cutter column, where the aldehydes were retained as the 
hydrocarbons were passed through and vented. The cutter column was 
then backflushed to a cryogenic trap, where the aldehydes were 
reconcentrated before introduction onto an analytic column. About ar 
hour was required for a complete analysis. The method has not been 
used by other workers. 

Preconcentration before direct analysis has also been 
investigated. Pellizzari 1 3 101 * has reported the collection of some 
higher-raolecular-weight aldehydes on Tenax-GC. After thermal 
desorption and reconcentration in a cryogenic trap, analysis is 
performed by gas chroma tography/mass spectrometry. The method 
provided poor quantification. Gold e_t al^ * successfully captured 
acrolein on molecular sieves. The sieves were desorbed with water, 
which was then injected onto a column packed with hydrophobia 
Tenax-GC. The method has not been used by other workers. 

Derivatization is an alternative technique that has been 
extensively investigated. Levaggi and Feldstein 78 introduced a 
method in which samples were collected with impingers containing 1% 
sodium bisulfite solution. Aldehydes react with the bisulfite to fori 



158 

adducts. Formaldehyde and acrolein are analyzed by chromo tropic acid 
and 4-hexylresorcinol methods, respectively. To analyze the remaining 
aldehyde, the bisulfite solution is injected onto a packed column in a 
gas chroma tograph. Samples must be kept cold to prevent 
deterioration. The Intersociety Committee 10 has adapted the 
technique as a tentative method for the ^-5 aldehydes, but there 
are no reported uses in the literature. A problem not explicitly 
discussed is the rapid degradation of column performance due to the in 
situ production of sulfur dioxide and sodium hydroxide as the adduct 
thermally decomposes. 

Much work has been aimed at using 2,4-dinitrophenylhydrazone 
(DNPH) derivatives of aldehydes, well known for many years for their 
use in the qualitative identification of aldehydes. DNPH reacts with 
aldehydes in aqueous solution to form precipitates. In most attempts, 
this precipitate is redissolved in an organic solvent, which is then 
injected into a gas chroma tograph. The resulting chroma tog rams show 
double peaks for each derivative corresponding to the syn- and anti- 
isomers formed around the nitrogen-carbon double bond characteristic 
of the derivative. These peaks are not symmetrical, because of steric 
influences during formation of the derivative. The peaks observed for 
the derivatives of propionaldehyde , acrolein, and acetone overlap and 
are difficult to separate. The most consistent problem is the 
verification that quantitative derivatization of the available 
aldehydes has occurred. 

DNPH was applied by Hoshika and Takata 55 to the analysis of 
automobile exhaust and cigarette smoke. Papa and Turner 101 102 also 
applied it to automobile exhaust. In a two-step process, preliminary 
separation of DNPH aldehyde derivatives by preparative gas 
chromatography was followed by analytic gas chromatography. 131 In 
analyzing food samples, a number of workers have used glutaric acid 
and flash-exchange gas chromatography to regenerate free aldehydes 
from DNPH derivatives. 50 si es 6? BO 109 

A variety of alternative derivatizing reagents have been 
investigated. Gas chromatography of aldehydic derivatives of 
phenylhydrazine 71 and 2,4,6-trichlorophenyl hydrazine 6 " has been 
studied. These reagents are close analogues of DNPH. The aldehydic 
derivatives of dimethylhydrazine, 6 3 hydroxylamine , 1% J and 
tetramethyl ammonium acetyl hydrazide (Girard-T Reagent) ^ "* 6 97 
have been analyzed with gas chromatography. Like DNPH, these reagents 
all involve reaction of a free amine with the formyl group to form a 
nitrogen-carbon double-bonded derivative. 

Direct analysis of aldehydes with high-performance liquid 
chromatography (HPLC) has not been thoroughly investigated, primarily 
because of the lack of a detector with sufficient sensitivity. To 
circumvent this problem, aldehydes can be made to react with DNPH to 
form a derivative with a strong ultraviolet-absorption spectrum. This 
approach has been investigated by Carey and Persinger , 29 Mansfield 
e_t_al_. , 87 Selim, 126 and others. 

Ion chromatography is a new technique (DIONEX, Inc., Sunnyvale, 
Calif.) that has application to formaldehyde analysis, it combines 
liquid chromatography with an ion-exchange column to separate charged 



159 

species. A conductivity detector provides excellent sensitivity. 
Formaldehyde is captured on specially impregnated charcoal and then 
desorbed with aqueous peroxide. The resulting formate ion can then be 
analyzed by ion chroma tog raphy. Two ma;jor difficulties with the 
method are ensuring quantitative recovery of formaldehyde from the 
charcoal and preventing the peroxide reagent from oxidizing other 
materials to formate ion. 



ELECTROCHEMICAL METHODS 

In addition to the usual techniques of analyzing organic 
materials, aldehydes can be analyzed by electrochemical methods. Both 
polarographic methods and amperometric titrations have been used. 

Lupton and Lynch 83 developed polarographic techniques for the 
analysis of aldehydes in a wide range of samples. McLean and 
Holland 89 adapted their technique to a portable system for rapid 
analysis of aldehydes in automotive exhaust sampled by bubbling into 
water. The polarograph was rendered portable by replacing the 
dropping mercury electrode with a quiescent mercury pool a few 
millimeters in diameter. Analysis used the method of standard 
additions. The procedure is not specific, however, even for aldehydes. 
The authors suggested differential-pulse polarography for separation 
of the aldehydes, but this has not been tested. 

Ikeda 61 developed a short-circuit argentometric amperometric 
titration for determining formaldehyde with a rotating platinum 
electrode. Equimolar amounts of acetaldehyde produced substantial 
interference, and other aldehydes may as well. The method is suitable 
for measuring quantities of formaldehyde as low as 0.1 mg. 



CURRENT APPLICATIONS OP ANALYTICAL METHODS 

The standard techniques for analysis of aldehydes in use today 
were developed for application in specific sampling situations. These 
situations and the techniques used are discussed below. 

AIR 
Ambient Air 

The wet-chemistry spectrophotometric methods of analysis have beei 
used extensively for the analysis of aldehydes in ambient air. The 
method based on MBTH has been applied to studies of total aliphatic 
aldehydes in the ambient atmosphere and from emission sources. 5 7 108 
As mentioned earlier, it has been recommended for the determination o 
total aliphatic aldehydes by the Intersociety Committee. 10 

Invariably in atmospheric or emission samples the principal 
aldehyde detected is formaldehyde. The most extensively used 
procedure is based on chromotropic acid. 6 ' 8 ll7 123 The 
Intersociety Committee 10 and NIOSH 139 have recommended the use of 



160 

chromotropic acid. Schiff's reagent (basic fuchsin) and 
pararosaniline also have been suggested for atmospheric 
determinations. 73 B * 110 

The high toxicity of acrolein has prompted analyses of this 
aldehyde in atmospheric and emission samples. The only sufficiently 
sensitive colorimetric method available for analysis of acrolein is 
based on 4-hexylresorcinol, 2 31 a reagent that has been used 7 112 123 
and is recommended by the Intersociety Committee. 10 A single 
investigation used a gas-chroma tographic technique to determine 
acrolein in ambient air. 18 



Gasoline and Diesel Exhaust 

The MBTH technique has been applied to automobile (gasoline) 1211 12S 
and diesel 111 exhaust emission to determine the concentration of 
total aliphatic aldehydes. Two titrimetric procedures have also been 
used for auto-exhaust measurements. 39 

The chromotropic acid method has been used widely for measuring 
formaldehyde in automobile 1 *- 6 8 7S 117 125 and diesel 1 " * el 82 
exhaust. The Schryver method, involving the reaction of formaldehyde 
with phenylhydrazine followed by oxidation with potassium femcyanide 
to form a red derivative, also has been used in studies of 
formaldehyde emitted in automobile and diesel exhaust. 38 39 

The acrolein content of automobile exhaust has been determined 
with the 4-hexylresorcinol method. 3 13 31 75 Diesel-exhaust emission 
has also been studied with this technique. 1 " 81 82 i11 

Because of the relatively high concentrations of acrolein 
encountered in automobile and diesel exhaust, this pollutant can be 
effectively measured by gas-chromatographic techniques. Acrolein has 
been determined directly and as a derivative. 18 " " 2 s9 60 12 " 



Nonoccupational Indoor Air 

Interest in measuring aldehyde concentrations in nonoccupational 
indoor environments is a relatively recent phenomenon. Workers in 
Europe were among the first to determine aldehyde and formaldehyde 
concentrations in residences. In the Dnited States, attention has 
been focused on formaldehyde emitted from urea-formaldehyde products 
used in the construction of homes, especially mobile homes. Table 5-3 
(in Chapter 5) summarizes the studies performed to date. 

Formaldehyde concentrations were determined for residences in 
Denmark, ^ the Netherlands, and the Federal Republic of 
Germany. 1 " 8 Maximal concentrations observed in European dwellings 
reached 2.3 ppm, but average concentrations were 0.4 ppm or less. 11 14 
Interestingly, maximal formaldehyde concentrations in residences built 
without formaldehyde-releasing materials in the Netherlands reached 
only 0.08 ppm, and average concentrations were only 0.03 ppm. 1 " 8 
Chromotropic acid was used most often in these European studies. 



161 

The MBTH technique was used to measure total aliphatic aldehydes 
in a pair of mobile homes and a sample residence in Pittsburgh. 93 
Breysse 21 * used the chromotropic acid method recommended by NIOSH to 
sample 608 mobile homes in the state of Washington in which residents 
had complained of irritation; the peak formaldehyde concentration 
observed in an occupied home was 1.77 ppm, and the mean was less than 
0.5 ppm. Garry et al. ** used the chromotropic acid method with a 
shortened sampling time to assess formaldehyde concentrations in 
Minnesota mobile homes. The state of Wisconsin also has used the 
chromotropic acid method to sample in mobile homes in which residents 
had registered complaints (M. Woodbury, personal communication) . 

Systematic studies of formaldehyde and total aliphatic aldehydes 
as pollutants in nonoccupational indoor environments have been 
performed by the Lawrence Berkeley Laboratory (LBL) (Lin et al. 79 
and Miksch e_t_ al_. , unpublished manuscript). LBL has used the MBTH 
technique to determine total aliphatic aldehyde concentrations f and 
the chromotropic acid technique and a modified pararosaniline 
technique have been used to measure formaldehyde. Sampling sites hav 
included conventional and energy-efficient homes (occupied and 
unoccupied) and public buildings, such as schools, office buildings, 
and hospitals. 



Occupational Indoor Air 

Only occupational air-quality formaldehyde standards are 
recommended or promulgated by several agencies and professional 
organizations in the United States. OSHA 1 * has promulgated an 8-h 
time-weighted average (TWA) standard of 3 ppm. The American 
Conference of Governmental Industrial Hygienists 9 has promulgated a 
threshold limit value (TLV) standard of 2 ppm. NIOSH 138 has 
recommended an exposure standard of no greater than 1 ppm for any 
30-min sampling period. 

The Intersociety Committee, 10 of which the ACGIH is a member, 
and NIOSH 139 both recommend a method of analysis for formaldehyde 
based on the use of chromotropic acid. Despite this recommendation, 
workers investigating formaldehyde concentrations in occupational 
environments have used a variety of techniques summarized in Table 5- 
(in Chapter 5) . 

Shipkovitz 127 investigated formaldehyde in textile plants where 
fabric was treated with formaldehyde-containing resins. Samples wer< 
generated by drawing air through bubblers containing sodium bisulfit* 
solution and were analyzed by iodometric titration. The method was 
reported to have a sensitivity of 0.5 ppm, but was not specific for 
formaldehyde. 

Collection in sodium bisulfite had been used earlier by the 
California Department of Public Health 21 to analyze air at a textile 
garment factory. The method of analysis was not reported. In the 
same year, however, the California Department of Public Health 
investigated airborne formaldehyde in a clothing store by using midg> 



162 

impingers containing a solution of MBTH. 9 1 As with sodium 
bisulfite, this reagent is not specific for formaldehyde. 

A modified chromotropic acid procedure was used by Schuck et 
aJL. 121 to determine formaldehyde concentrations during a study of 
the ocular effects induced by smog components. Subjects were exposed 
to formaldehyde in a smog chamber. Chromotropic acid was used to 
determine formaldehyde concentrations between 0.04 and 10.9 ppm at two 
laminating plants using phenol-resorcinol glues. 1 * 1 * A survey of six 
funeral homes used a modified chromotropic acid procedure, in which 
air was bubbled into 0.1% chromotropic acid in concentrated sulfuric 
acid, to determine exposure to formaldehyde during the embalming 
process. 69 Reported concentrations of 0.09-5.26 ppm may have been 
in error on the high side, inasmuch as no prefilter was used on 
air-sampling lines to remove paraformaldehyde dust which was also 
present. 



WATER 

Most of and perhaps all the methods that have been used to 
identify or measure aldehydes in samples of air and biologic tissue 
should be applicable to water samples; however, little research has 
been performed to determine the relative accuracy, precision, or 
sensitivity of the methods for measuring aldehydes in water. 

Because of the high toxicity of acrolein to aquatic life, Kissel 
and co-workers 70 evaluated several chemical analytical procedures by 
comparing the analytical data with data from bioassays on acrolein. 
Eight methods three derivatization and five direct were evaluated. 
The derivatization methods were the bromide-iodide-thiosulfate 
titration method of Pressman and Lucas, 106 the 2,4-dinitrophenyl- 
hydrazine colorimetric method of Bowmer and co-workers, 22 and the 
aminophenol fluorescence method of Alar con. J Direct measurements 
were performed by ultraviolet spectrophotometry, 1 * 9 gas-liquid 
chroma tography, 13 nuclear-magnetic-resonance spectroscopy, 
differential-pulse polar ogr aphy, 5S and direct fluorescence. The 
effect of different buffering systems on the toxicity and chemical 
analysis of acrolein was also investigated. 

Analytical data produced by the derivatization methods and by 
gas-liquid chromatography did not correlate well with the bioassay 
data. Often, no biologic responses were observed for test solutions 
in which these methods indicated the presence of toxic concentrations 
of acrolein. The direct ultraviolet spectrophotometric method was 
also judged unsuitable, because it produced extraneous peaks, which 
were often more intense than the acrolein peaks and tended to mask 
them. 

Data producted by nuclear-magnetic-resonance spectroscopy, 
differential-pulse polarography, and direct fluorescence correlated 
very well with the bioassay data. Assuming that the bioassay provided 
a more realistic measure of the concentrations of acrolein in 
solution, the authors concluded that these direct methods were 
suitable for monitoring acrolein in water. How well these methods 



163 

will work for other aldehydes is unknown. Unfortunately, this study 
appears to be the only published one concerning the suitability of 
possible methods for measuring an aldehyde in water. 

Gas chromatography, in combination with mass spectroscopy, appear 
to be gaining favor over other techniques for identifying and 
measuring aldehydes not only in water, but in plant material where 
the chemical composition can be highly complex, which necessitates tt 
isolation of the aldehyde from other components. Problems have been 
encountered, however, when conventional gas-chroma tographic procedure 
(such as use of packed columns) are used. Such columns are incapabl* 
of resolving all the aldehydes present. For this reason, some 
investigators have resorted to using thin-layer chromatography in 
conjunction with gas chromatrography to obtain greater resolution. 

The advent of the glass capillary column has essentially 
eliminated the need for thin-layer/gas chromatography. Hollowell 
(personal communication) used a gas chroma tog raph (Carlo Elba) 
equipped with a 50-m 3 glass capillary column and a splitless 
injector system in conjunction with a mass spectrometer (Finnigan, 
Model 3200) to identify and measure aldehydes in drinking water of 
various sources. The aldehydes were removed from the water samples 
and concentrated in XAD columns (resin series not designated). The 
eluting solvent was not reported, but presumably was benzene or ethy 

acetate. 

Although the gas-chromatographic system provided excellent 
separation of the aldehydes, the electron-impact mass-spectroscopic 
technique was not suitable for determining the exact structure (and 
therefore identifying) a number of compounds with an apparent alkana 
structure. With the system, Piet was able to identify 13 aldehydes; 
their concentrations ranged from 0.005 to 0.3 ppb. 



P^LANT MATERIAL 

Two analytical methods have been used for measuring aldehydes, c 
involving gas chromatography and the other, DNPH formation. For fri 
products, an open tubular gas-chromatographic column with programed 
temperature control has been used to separate volatile components, 
stainless-steel tube coated with GE SF-96 (50-silicone) was used wi 
grape juice. A copper tube packed with 10% Carbowax 20M on Halopori 
was used in research with ginkgo leaves. A combination of infrared 
spectra, retention data, and mass spectrometry was used to identify 
and measure particular aldehydes. 

in 1972, Major and Thomas 86 compared the amount of 2-hexenal in 
ginkgo leaves as measured by gas chromatrography and by the weight 
2,4-DNPH. He added the ether extracts of steam-distilled leaves to 
solution of 2,4-DNPH, hydrochloric acid, and methyl alcohol. After 
h, the solvents were evaporated to a small volume, and the 
crystallized 2,4-DNPH was checked for purity by melting point and b 
thin-layer chromatography (TLC) on silica gel with 6:1 hexanerether 



164 

as the developer. Recovery by DNPH was inferior to that by the 
gas-chromatographic method. 

Winter and Sundt, 1 " 7 leaders in investigation of strawberry 
flavors, have objected to the use of gas chroma tog raphy in aldehyde 
analysis, because it operates at a relatively high temperature and 
product modifications may result under these conditions. They favor 
paper chroma tog raphy, because the volatile constituents are fixed 
rapidly by derivative formation and thus protected from further 
changes. They have identified the isolated derivatives by melting 
point and by infrared spectroscopy. 

In 1976, Braddock and Kesterson 23 used a more sophisticated 
2,4-DNPH method than reported by Manor and Thomas. Cold-pressed 
citrus oils dissolved in hexene were applied to a bed of a 2,4-DNPH 
reaction column. A volume of about 500 ml was eluted and aliquots 
were chromatographed on consecutive columns of Celite-Seasorb and 
alumina. Column effluents were evaporated to dryness and taken up in 
chloroform, and the absorbence was determined for estimation of 
quantities of 2,4-DNPH by the extinction coefficients. Effluents from 
the alumina columns were separated by thin-layer chromatography into 
individual aldehyde 2,4-DNPHs. Each aldehyde was scraped from the TLC 
plates and measured by its extinction coefficient. Tentative 
identification of individual aldehyde 2,4-DNPHs was by comparison of 
Rf values with standard derivatives. Aldehyde 2,4-DNPHs scraped 
from TLC plates were identified positively by comparing mass spectra 
of known derivatives with the unknowns. 



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101. Papa, L. J., and L. P. Turner. Chromatographic determination of 
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103. Pellizzari, E. D. Development of Analytical Techniques for 
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105. Pinigina, I. A. Use of 2,4-dinitrophenylhydrazine for 
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106. Pressman, D. , and H. J. Lucas. Hydration of unsaturated 
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107. Pyne. A. W. , and E. L. Wick. Volatile components of tomato. J. 
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108. Radian Corporation. Houston Area Oxidants Study. Report No. 
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109. Rails, J. W. Higher recoveries of carbonyl compounds in flash 
exchange gas chroma tog raphy of 2,4-dinitrophenylhydrazones. 
Anal. Chem. 36:946, 1964. 

110. Rayner, A. C., and C. M. Jephcott. Microdetermination of 
formaldehyde in air. Anal. Chem. 33:627-630, 1961. 

111. Reckner, L. R. , W.E. Scott, and W. F. Biller. The composition 
and odor of diesel exhaust. Proc. Am. Petrol. Inst. 45: 
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112. Renzetti, N. A., and R. J. Bryan. Atmospheric sampling for 
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113. Roffael, E. Formaldehyde Release from Particleboard Methods of 
Determination. Presented at the Consumer Product Safety 
Commission Technical Workshop on Formaldehyde, Washington, D.C. , 
April 1980. 



172 

114. Sawicki, E. f and R. A. Carnes. Spectrophotofluorimetric 
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Mikrochim. Acta 1968:148-159, 1968. 

115. Sawicki, E., and T. R. Hauser. Spot test detection and 
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118. Sawicki, E., T. W. Stanley, and J. Pfaff. Spectrophoto- 
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119. Scaringelli, F. P., A. E. O'Keefe, E. Rosenberg, and J. p. 
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120. Schiff, H. Eine neue Reithe organisher Diamine. Ann. Chem. 
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122. Schuette, F. J. Plastic bags for collection of gas samples. 
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173 

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174 

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1966. 



CHAPTER 7 
HEALTH EFFECTS OF FORMALDEHYDE 



There is an increasing body of evidence that the exposure of the 
human population to formaldehyde vapors may be the source of the many 
complaints related to irritation of the eyes and respiratory tract, 
headache, tiredness, and thirst; these symptoms have been reported by 
occupants of homes, schools, and industrial buildings mainly by 
residents of homes in which formaldehyde has been detected at high 
concentrations. Owing to the common use of formaldehyde in building 
materials and in foam insulation, there is a potential for exposure of 
employees engaged in the manufacture of these products and for 
exposure of the general public using the products. Furthermore, there 
are many workers in a great variety of occupations who, through the 
use of formaldehyde and its associated products, may be exposed to 
formaldehyde at high concentrations in the course of a day's work (see 
Table 7-1) . Energy-conservation measures that have become widely used 
in recent years, including reduced ventilation rates, have led to 
increased indoor formaldehyde concentrations .2126 We have 
considered in some detail (in Chapter 5) these and the many other 
sources of formaldehyde pollution in our environment today. In view 
of the widespread use of formaldehyde and the large number of people 
who are exposed to it, we must be concerned about the potential health 
effects associated with these exposures. 

Because of the unique importance of formaldehyde among the many 
aldehydes in use today, we devote this chapter to its consideration. 
The health effects of the several other important aldehydes are 
discussed in Chapter 8. Eye irritation and respiratory tract 
irritation are common results of human exposure to formaldehyde at 
relatively low concentrations. Documented cases of hypersensitivity 
with bronchial asthma due specifically to formaldehyde are few; more 
commonly, asthma is aggravated by the irritating properties of 
formaldehyde. Aqueous solutions damage the eye and irritate the skin 
on direct contact. Repeated exposure to dilute solutions may lead to 
allergic contact dermatitis. Systemic formaldehyde poisoning by 
ingestion is uncommon, because its irritancy makes ingest ion 
unlikely. We discuss here the preliminary findings of a Chemical 
Industry Institute of Toxicology (CUT) study with regard to 
formaldehyde induction of nasal cancer in rats and mice. The human 
carcinogenic, mutagenic, and teratogenic potential of formaldehyde is 

175 



176 

TABLE 7-1 
Potential Occupational Exposures to Formaldehyde 2 



Anatomists 
Agricultural workers 

Bakers 

Beauticians 

Biologists 

Bookbinders 

Botanists 

Crease-resistant-textile 

finishers 
Concrete users 

Dentists 

Deodorant makers 

Dialysis technicians 

Disinfectant makers 

Disinfectors 

Dress-goods store personnel 

Dressmakers 

Drugmakers 

Dry cleaners 

Dyemakers 

Electric-insulation makers 
Emb aimers 

Embalmin-fluid makers 
Ethylene glycol makers 

Fertilizer makers 
Fireproofers 

Formaldehyde-resin makers 
Formaldehyde workers 
Fumlgators 
Fungicide workers 
Furniture dippers and sprayers 
Fur processors 



Glass etchers 

Glue and adhesive makers 

Hexamethylenetetramine makers 
Hide preservers 
Histology technicians 
Home construction workers 

Ink makers 

Lacquerers and lacquer makers 
Laundry workers 

Medical personnel 
Mirror workers 

Oil-well workers 

Paper makers 
Pentaerythritol makers 
Photographic-film makers 

Resin makers 
Rubber makers 

Soil sterilizers and green- 
house workers 
Surgeons 

Tannery workers 

Taxidermists 

Textile mordanters and printers 

Textile waterproofers 

Varnish workers 
Wood preservers 



Modified from NIOSH. 198 



177 

not known, but it has exhibited mutagenic activity in a wide variety 
of organisms. 



ASSESSMENT OF ADVERSE HEALTH EFFECTS 

Adverse health effects due to formaldehyde may occur after 
exposure by inhalation, ingestion, or skin contact. It is difficult 
to ascribe specific health effects to specific concentrations of 
formaldehyde to which people are exposed, because they vary in their 
subjective responses and complaints. Moreover, persons with disease 
may be more responsive to low concentrations than hyposensitive 
persons who do not respond to the same concentrations. Thus, the 
threshold for response will not be constant among all segments of the 
population. Also, studies done in homes, both mobile and 
conventional, where the subjective complaints of consumers reportedly 
can be ascribed to formaldehyde (especially when only formaldehyde is 
measured) may not be completely valid, because other pollutants acting 
independently may cause the same symptoms or synergistically may 
enhance the perception of symptoms. (See Chapter 5 for factors that 
affect the outgassing of formaldehyde.) Interpretation of the health 
effects of formaldehyde must consider not only the concentration, but 
also the duration of exposure of subjects. For example, in some 
studies, exposures lasted only a few minutes; 81 90 132 17S 207 in 
others, they lasted several hours 72 137 179 183 or days. 215 2l7 A 
short-term inhalation study cannot accurately predict the effects of 
formaldehyde on persons who reside in homes where there is a 
continuous low-dose exposure. Tolerance may develop after several 
hours of exposure 15 loz 173 and modify the response to 
formaldehyde. In some persons not previously sensitized, repeated 
exposure to formaldehyde may result in the development of 
hyper sensitivity. 

Analytical procedures for formaldehyde vary in both sensitivity 
and specificity (see Chapter 6) . * 29 31 as ss 82 us ne 136 isa 

158 159 166 177 178 186 216 



BIOCHEMISTRY AND METABOLISM OF FORMALDEHYDE 

Formaldehyde is a normal metabolite and a vital ingredient in the 
synthesis of essential biochemical substances in man and thus in small 
quantities is not toxic. 39 109 Formaldehyde controls a 
rate-limiting step in the processing of methyl groups derived from the 
metabolic dealkylation of O-, N-, and S_-methyl compounds during their 
detoxification and excretion. 209 With ample dietary supplies of 
tetrahydrofolic acid, vitamin B-j^ r and such sulfhydryl compounds as 
cysteine and methionine, small amounts of formaldehyde are readily 
metabolized. 

Formaldehyde also is involved in lipid metabolism in the 
decomposition of peroxides by catalase. 203 



178 

The biochemical transformations of endogenous and exogenous 
formaldehyde are similar and involve coenzymes and hydrogen transport 
systems that are normally present in all animals and bacteria. 39 " 109 
Interspecies variations in the metabolism of formaldehyde may account 
for differences in reaction rates in these systems. 55 75 7 205 209 
Formaldehyde oxidation, for example, is greater in human liver than in 
rat liver; this may explain the unique susceptibility of man to 
methanol poisoning. 18S 

The main reaction of formaldehyde appears to be an initial 
oxidation to formic acid in the liver and erythrocytes. 39 5S " 103 109 12t 
Once formic acid is formed, it can undergo three reactions: oxidation 
to carbon dioxide and water, elimination in the urine as a sodium 
salt, or entrance into the metabolic one-carbon pool. Formaldehyde 
may also enter the one-carbon pool directly. 

In man, the formation of formate from formaldehyde appears to 
involve an initial reaction with glutathione to form a hemiacetal . 7 5 18I 
The enzyme formaldehyde dehydrogenase (FDH) then oxidizes the 
hemiacetal to formic acid, with NAD as a hydrogen acceptor. 55 18 * 
In humans, FDH is a multifunctional complex of enzymes that converts 
methanol to formic acid without releasing formaldehyde as an 
intermediate, 75 18t| 202 206 inasmuch as it is difficult to isolate 
FDH alone. 

The molecular weight of human FDH is 81,400, and that of rats is 
111, 000. 7S 20Z Human liver FDH activity is 50% greater than that of 
rat liver, in terms of enzyme units per gram of liver. 75 The actual 
product of the human FDH reaction is not free formic acid, but 
-formylglutathione, which hydrolyzes slowly in human liver 
preparations to formate. 202 

Tran e_t al_. 191 investigated the uptake of [ 14 C] formaldehyde 
and its conversion to carbon dioxide by erythrocytes from chronic 
alcoholics and nonalcoholics. The ingestion of ethanol initially 
decreased the rate of carbon dioxide production from formaldehyde in 
both groups, but a greater decrease was noted in the alcoholics' 
erythrocytes. A few hours later, the erythrocytes from alcoholics had 
a carbon dioxide production rate well above their baseline values; the 
rate returned to normal several days later. These findings could be 
explained on the basis that ethanol interfered with tetrahydrofolic 
acid activity during metabolism. The potential interference with 
tetrahydrofolic acid activity brings up the theoretical possibility 
that formaldehyde affects folate uptake by cells. Tetrahydrofolic 
acid is important, in that an induced folate deficiency may result in 
a number of medical conditions, including hematologic abnormalities 
and neurologic and growth effects in infants. 12 17 121 12e 17 A 
folate-dependent one-carbon pathway was found to be primarily 
responsible for formate oxidation in monkeys poisoned with 
methanol. 130 Formate elimination from the blood of folate-def icient 
monkeys was about half that of controls. 

It has been reported that formaldehyde causes the eye effects and 
formic acid some of the acidosis seen in methanol poisoning. 33 
Although in vitro studies indicate that formaldehyde has significant 
effects on retinal oxidative phosphor ylat ions, l it is rapidly 



179 

metabolized to formic acid in humans, dogs, cats, rabbits, guinea 
pigs, rats, and monkeys. 131 16 Formaldehyde is eliminated from the 
blood with a half-life of 1-2 mm. in a study of formate-poisoned 
monkeys, there was no detectable increase in formaldehyde 
concentration in samples of blood, urine, cerebrospinal fluid, 
vitreous humor, freeze-clamped liver (at the temperature of liquid 
nitrogen), kidney, optic nerve, or brain, 12 " 131 at a time when 
formate concentrations were high. In a recent report of methanol 
poisoning in humans, formate accumulation was marked; that indicates 
that formic acid plays a major role in the acidosis in human 
poisonings. 12 9 

Some adverse effects of formaldehyde may be related to its high 
reactivity with amines and formation of methylol adducts with nucleic 
acids, histones, proteins, and amino acids. The methylol adducts can 
react further to form methylene linkages among these reactants. 11 
118 It appears that before formaldehyde reacts with amino groups in 
RNA, the hydrogen bonds forming the coiled RNA are broken. 61 * 1>tS 
Formaldehyde reacts with DNA less frequently than with RNA, because 
the hydrogen bonds holding DNA in its double helix are more stable. 6 " 
172 Reaction of formaldehyde with DNA has been observed, by 
spectrophotometry and electron microscopy, to result in irreversible 
denaturation. In reactions with transfer RNA, formaldehyde interferes 
with amino acid acceptance. 11 172 The equilibrium reaction of 
formaldehyde with DNA involves thermally activated opening and closing 
of hydrogen bonds between matching base pairs in the helix. 172 If 
permanent cross links are formed between DNA reactive sites and 
formaldehyde, these links could interfere with the replication of DNA 
and may result in mutations. When human fetal lung fibroblasts were 
incubated with tracer amounts of -^C-labeled formaldehyde and 
acetaldehyde, l 55 a pulse of 10 rain with formaldehyde followed by a 
6-min and 24-h chase showed migration of carbon-14 into the nucleus. 
Fractionation of the nucleus revealed that the RNA fraction had the 
highest absolute and specific activity, whereas the DNA and protein 
fractions had considerably lower activity. All the counts from 
formaldehyde were found in the adenine and guanine components of RNA. 
The DNA count was distributed among adenine, guanine, and thymine. 



EFFECTS IN ANIMALS 
ACUTE TOXICOLOGY STUDIES 

When administered orally, formaldehyde (formalin) is slightly 

toxic in rats, with LDsp values reported in the range of 500-800 
rag/kg. 179 193 When administered by inhalation, it is moderately 
toxic in rats, with 3-min and 4-h LCsgS of 815 and 479 ppm, 
respectively. 138 llfl Pulmonary edema was the predominant pathologic 
change. Similar results were obtained in cats and mice. 

Formaldehyde causes mild to moderate irritation when applied to 
rabbit skin at 0.1-20% (Haskell Laboratory, Du Pont Company, 
unpublished data) . Formaldehyde was also administered to nine guinea 



180 

pigs intradermally or topically over a 2-wk period. After a 2-wk rest 
period, they were challenged with formaldehyde; five of the animals 
had become sensitized. Dermal sensitization by airborne formaldehyde 
has not been reported. 

Formaldehyde is a severe eye irritant. Experimental application 
of 0.005 ml of 15% formalin to rabbit eyes caused a severe 
reaction corneal and conjunctival edema and iritis graded 8 on a 
complex injury-grading scale of 1-10. 32 Exposure of rabbits to 
formaldehyde vapors at 40-70 ppm caused slight tearing and eye 
discharge, but not corneal injury. 78 



EXTENDED TOXICOLOGY STUDIES 

Continuous 90-d inhalation studies have been conducted with 
several species of laboratory animals. In one study, rats, guinea 
pigs, rabbits, monkeys, and dogs were exposed to formaldehyde at 3.7 
ppm. 1 * One of the exposed rats died, but there were no overt signs 
of toxicity. Various degrees of interstitial inflammation were seen 
in the lungs of all the exposed animals, and there was focal chronic 
inflammation in the hearts and kidneys of the rats and guinea pigs. 
It was uncertain whether these changes were compound-related, in 
another study, groups of 25 rats were continuously exposed at 1.6, 
4.55, or 8.07 ppm for 45-90 d. 50 The only adverse effect at 1.6 ppm 
was discoloration of the hair. The 4.55-ppm group was exposed for 45 
d and had a decrease in rate of weight gain. The 8.07-ppm group was 
exposed for 60 d and had respiratory and eye irritation, a decrease in 
food consumption, and a decrease in liver weight. 

In a noncontinuous inhalation study, groups of 20 mice and 20 rats 
were exposed to formaldehyde at 4, 12.7, or 38.6 ppm, 6 h/d, 5 d/wk, 
for 13 wk (Chemical Industry Institute of Technology, unpublished 
data). No adverse effects were observed in the 4-ppm group. At 12.7 
ppm, a decrease in body weight and evidence of nasal erosion in two 
exposed rats were observed. Dlceration and necrosis of the nasal 
mucosa seen at 38.6 ppm resulted in termination of exposure after 2 
wk. Groups of 60 mice were exposed at 41 or 82 ppm, 1 h/d, three 
times a week, for 35 wk." The 41-ppm group was then exposed at 123 
ppm for 29 wk. All the groups tolerated the exposure reasonably well, 
and the average weight of the mice rose normally. Pathologic 
examination of the tracheal epithelium revealed basal cell 
hyperplasia, squamous cell metaplasia, and atypical metaplasia. 
Extension of metaplasia into the major bronchi was infrequent, except 
in the animals that were exposed at 123 ppm. In these animals, the 
metaplastic changes in the epithelium appeared to extend farther into 
the major bronchi with increasing exposure. Exposure of a similar 
group of mice at 163 ppm was terminated after 11 d, because of severe 
pathologic changes and deaths. 

The Formaldehyde Institute is sponsoring studies at Biodynamics, 
Inc., on effects of virtually continuous inhalation of formaldehyde in 
monkeys, hamsters, and rats. These are daily 22-h exposures at 3, 1, 
and 0.2 ppm that are repeated for 26 wk. Results of gross and 



181 

microscopic evaluation of animals exposed at 0.2 and 1.0 ppm (now 
completed) showed no treatment-related effects. Final results (C. F. 
Reinhardt, personal communication) on animals exposed at 3 ppm have 
shown no adverse effects in hamsters; in rats and monkeys, there is 
histologic evidence of squamous metaplasia of the nasal mucosa in 
exposed animals. The hamsters showed no histologic changes at any of 
the exposure concentrations. 



RESPIRATORY SYSTEM EFFECTS 

Formaldehyde is readily soluble in the mucous membranes of 
animals. Respiratory tract uptake is almost 100% in dogs. 52 When 
inhaled by guinea pigs for 1 h at 0.3-50 ppm, formaldehyde increased 
airway resistance and decreased compliance. These effects were 
reversible at concentrations less than 40 ppm and were not seen 1 h 
after exposure. Guinea pigs exposed for 1 h at 3.5 ppm had a 40% 
increase in airflow resistance and a 12% decrease in compliance. The 
increase in resistance was dose-related over the range of 0.25-50 ppm; 
tracheal cannulation doubled the increase in resistance. The 
combination of formaldehyde and sodium chloride aerosol (0.04 vim in 
diameter) at 10 mg/m 3 further increased airway resistance. 6 

In another study, 25 rats each were exposed continuously for 3 mo 
at 0.0098, 0.028, 0.82, and 2.4 ppm. At 2.4 ppm, there was a 
significant decrease in cholinesterase activity; at 2.4 and 0.82 ppm, 
there were proliferation of lymphocytes and histiocytes in the lungs 
and some peribronchial and perivascular hyper emia. There were no 
significant findings at the two lower concentrations. 

The effects of formaldehyde exposure on respiratory rate were 
studied in mice. Exposure for 10 mm at 3.1 ppm, 3 h/d, for 3 d 
before exposure at a higher challenge concentration (0.55-13.4 ppm) 
produced the same response as in a previously un exposed group. Similar 
exposure at concentrations higher than 3.1 ppm caused an increased 
response. However, accommodation occurred during each exposure 
period, with the respiration rate approaching normal. 98 Other 
research has shown formaldehyde to decrease ciliary transport within 
10 min at concentrations of 20-100 ppm. 1 * 2 * s 



CARDIOVASCULAR SYSTEM EFFECTS 

Large doses of formaldehyde have a vasopressor effect (increased 
blood pressure) in anesthetized mice. Smaller doses lead to a 
depressor response. Qualitatively, the responses are similar to that 
seen with acetaldehyde. 53 Dogs do not have such responses to 
formaldehyde. Other results from the same study suggest that an 
initial decrease in blood pressure is caused by alterations in the 
sympathetic nervous system. A later, more marked decrease may be the 
result of a direct effect on vascular smooth muscle. 187 



182 
MUTAGENIC POTENTIAL 

Numerous studies have been conducted to determine the mutagenicity 
of formaldehyde, and Auerbach et^ al_. 1 1 have reviewed the subject 
extensively. Formaldehyde has exhibited mutagenic activity in a wide 
variety of organisms, but the mechanism of formaldehyde mutagenesis 
has not been resolved. Formaldehyde may cause mutations by reacting 
directly with DMA; by forming mutagenic products on reaction with 
ami no groups on simple amines, ammo acids, nucleic acids, or 
proteins; or by forming peroxides that can react directly with DNA or 
indirectly by free-radical formation. 

Mutagenic activity has been detected in E_. coli * * and 
Pseudomonas fluorescens, s 8 but not in the Ames strains of Salmonella 
typhimurium. 106 Sasaki and Endo reported that the mutagenicity of 
formaldehyde was very weak and appeared only within a limited range of 
concentration in which the Ames test was modified slightly by 
preincubating for 15 min at 37C before charging the plates. 165 
Weak mutagenic activity was observed when the fungi Neurospora crassa 
and Aspergillus^ nidulans were treated. The increase in mutagenic 
activity observed in these studies after treatment in the presence of 
catalase inhibitors suggested that peroxides were involved in the 
induction of mutations. Formaldehyde induced mitotic recombination in 
Saccharomyces cerevisiae. 3I Recently, formaldehyde was shown to 
induce mutations and cause DNA damage and repair in Saccharomyces. 35 117 lie 
The studies concerning formaldehyde mutagenesis in Drosophila have 
been reviewed by several authors. 11 l56 1B1 Mutations were induced 
in male larvae fed formaldehyde-containing food and in adults given 
injections of aqueous solutions of formaldehyde. The exposure of 
adults or larvae to formaldehyde vapors has not produced mutations. 
In one of five species of grasshoppers, formaldehyde caused 
chromosomal damage. 120 Germinating barley seeds soaked in 
formaldehyde solutions did not give evidence of mutations on 
maturation. sl * 

The mutagenic potential of formaldehyde in mammalian systems has 
not been thoroughly studied. An increase in mutation frequency was 
observed when formaldehyde was tested in the L5178Y mouse lymphoma 
assay. 37 76 Formaldehyde increased the mutation frequency in each 
of the four experiments conducted. However, a clear dose-response 
relationship was evident in only one of four experiments. No mutagenic 
activity was reported when formaldehyde was tested in the Chinese 
hamster ovary cell/HGPRT assay. 93 The data and a description of the 
treatment conditions have not yet been published. No effect was 
observed in limited dominant-lethal studies in which Swiss mice were 
given intraperitoneal injections of formaldehyde, 59 but many other 
mutagens were inactive in this series of tests. 

Formaldehyde has mutagenic activity in a variety of microorganisms 
and in some insects. Work is necessary to ascertain its mutagenic 
potential in in vitro cultures of germinal or somatic mammalian 
cells. Such information would be used in evaluating the hazard to 
humans exposed to formaldehyde. 



183 
EMBRYOTOXIC AND TERATOGENIC POTENTIAL 

Formaldehyde has not been shown to be teratogenic in animals. 
Pregnant dogs were fed diets containing formaldehyde (formalin in 40% 
solution) at 125 or 375 ppm on days 4-56 of gestation. None of the 212 
pups examined showed anomalies. Some of these pups were returned to 
the breeding colony, and their offspring showed no abnormalities. 95 

Rats were continuously exposed at 0.01 or 0.8 ppm for 20 d. 
Halfway through the exposure period, the animals were mated. No gross 
abnormalities were observed in the offspring, but there was an 
increase in gestation time. The number of fetuses decreased with 
increased formaldehyde concentration. However, the actual numbers of 
offspring in the 0.8-ppm, 0.01-ppm, and control groups were 208, 235, 
and 135, respectively. No explanation was given for the large 
increase in offspring from the exposed rats, compared with 
controls. 73 In another study, rats were exposed at 4.1 ppm for 4 
h/d on days 1-19 of pregnancy. No effect on the course of pregnancy 
or malformations in the fetuses were seen. 171 No alteration of 
reproductive function was seen in male rats given formaldehyde at 0.1 
ppm in their drinking water and 0.4 ppm in the air for 6 mo. 80 

In a gavage study, pregnant outbred albino mice were fed 
formaldehyde on days 6-15 of gestation. 123 The mice were sacrificed 
on day 18; the general health and reproductive status of the dams were 
evaluated, and the fetuses were examined for external, visceral, and 
skeletal malformations. The formaldehyde, which contained 12-15% 
methanol as a preservative, was lethal to 22 of 34 dams treated with 
185 mg/kg per day and one of 35 dams treated with 148 mg/kg per day. 
These doses did not produce statistically significant teratogenic 
effects in the fetuses of the surviving dams (two-sided p_ < 0.05, 
compared with controls) . 

When dogs were fed hexaraethylenetetramine (which decomposes to 
formaldehyde and ammonia in acid media) at 600 and 1,250 ppm on days 
4-56 of gestation, no evidence of teratogenesis was observed. And 
long-term feeding studies in rats given 1,600 ppm showed no effect on 
reproductive capacity. 95 



CARCINOGENIC POTENTIAL 

A 90-d pilot study of formaldehyde was conducted by the CUT 
(unpublished data) . Rats and mice were exposed to atmospheres 
containing formaldehyde at 4, 12.7, or 40 ppm. The exposures were 
conducted approximately 6 h/d, 5d/wk, for 13 wk (12 wk for the highest 
concentration) . Other animals served as controls and were exposed 
only to clean, filtered air. Exposure at 40 ppm resulted in 
ulceration or necrosis of nasal turbinate mucosa in significant 
numbers of animals of each species. Rats of both sexes had a high 
incidence of tracheal mucosal ulceration and necrosis; only a few male 
mice exhibited this lesion. Pulmonary congestion was prominent in 
both male and female rats and male mice at the high dosage. Female 
mice in the control and high-dosage groups had a similar incidence of 



184 

pulmonary congestion. Secondary lesions encountered in rats exposed at 
40 ppm were apparently related to bacterial septicemia after severe 
damage to respiratory tract mucosa. It was concluded that exposure at 
40 ppm was lethal, but that exposure at 12.7 ppm was not lethal and 
should be tolerable for an extended period. The pilot study was 
followed by a study of Fischer 344 rats and B6C3F1 mice described in 
the following abstract: 185 

Groups of 120 male and 120 female rats were exposed by 
inhalation to 0, 2, 6, or 15 ppm formaldehyde vapor 6 
hr/day, 5 days/week, for 18 months of a 24-month study. 
The present communication describes interim findings based 
on data available after 18 months of exposure. Squamous 
cell carcinomas occurred in the nasal cavities of 36 rats 
exposed to 15 ppm formaldehyde. The tumors ranged from 
small early carcinomas of the nasal turbinate to large 
invasive osteolytic neoplasms which extended into the 
subcutis of the premaxilla. Similar tumors were not 
detected in rats exposed for 18 months to 2 or 6 ppm or in 
mice exposed to 2, 6, or 15 ppm formaldehyde. Rhinitis, 
epithelial dysplasia, and squamous metaplasia occurred in 
rats from all exposure levels of formaldehyde; however, the 
severity and extent of the lesions were dose related. In 
contrast, papillary hyperplasia and squamous atypia 
occurred only in animals exposed to 15 ppm formaldehyde. 

This is the first experimental study to implicate formaldehyde as 
a potential carcinogen, but the significance of these preliminary 
findings can be evaluated only after completion of the study and 
analysis of the pathologic findings. (The CUT reported at the 
Formaldehyde Symposium on November 20-21, 1980, in Raleigh, N.C., that 
nasal cancer had been observed in rats exposed at 6 ppm for 24 mo and 
in mice exposed at 15 ppm for 24 mo.) 

Mice (strain C3H) exposed to formaldehyde at 83 ppm, for 1 h/d, 3 
d/wk, for 35 wk or at 41.5 ppm for 1 h/d, 3 d/wk, for 35 wk and at 125 
ppm for an additional 29 wk had basal cell hyperplasia and squamous 
cell metaplasia in the tracheobronchial epithelium, but no 
tumors. 91 Hamsters exposed at 10 ppm for 5 h/d, 5 d/wk, for their 
lifetime (average, 18 mo) had increased cell proliferation and 
hyperplasia in the lungs (P. Nettesheim, unpublished data); weekly 5-h 
exposures at 50 ppm for lifetime (18 mo) produced squamous metaplasia, 
but no tumors. In neither of these studies was nasal tissue 
specifically examined. 

Injection-site sarcomas developed in two of 10 rats given weekly 
injections of 0.4% aqueous formaldehyde for 15 mo. 20a Fibrosarcomas 
were observed in the liver and omentum in two other rats. These 
results are not useful, because of lack of controls and 
inappropriateness of the route of administration. 

A. R. Sellakumar et al. (personal communication) exposed 
Sprague-Dawley rats to hydrogen chloride at a mean concentration of 
10.6 ppm and formaldehyde at 14.7 ppm for 6 h/d, 5 d/wk, for their 
lifetime. Before dilution to the stated concentrations in the 



185 

exposure chamber, the initial reaction mixture had average hydrogen 
chloride and formaldehyde concentrations of about 6,500 and 1,000 ppm, 
respectively; alkylating-agent activity of 1.8 ppm was also detected, 
possibly as a result of the interaction of hydrogen chloride and 
formaldehyde in the gas phase. Alkylating-agent activity in the 
animal exposure chamber, as measured by chroma tog raphy, was 0.028 
ppm. Of the 99 exposed animals, 25 developed squamous cell carcinomas 
of the nasal epithelium. 169 No squamous cell tumors were observed 
in controls. One of the alkylating agents identified in the chamber 
was bis (chloromethyl) ether (BCME) , at a concentration of less than 1 
ppb. BCME is a potent carcinogen; esthesioneuroepitheliomas of the 
nose, squamous cell carcinomas of the lung and nasal turbinates, and 
adenocarcinomas of the lung and nasal cavity have been produced in 
rats after 10-100 exposures to BCME at 0.1 ppm for 6 h/d, 5 d/wk. 10fl 

Published reports indicate that BCME should not be formed in 
substantial amounts during chronic animal studies if concentrations of 
both hydrogen chloride and formaldehyde are less than 100 ppm at 
ambient temperature and humidity. 97 I89 However, Frankel et al. 67 
studied the reactions of formaldehyde and hydrogen chloride in the 
formation of BCME in glass vessels. They found that BCME is formed at 
less than 0.5 ppb when formaldehyde and hydrogen chloride are each 
present at 20 ppm, at less than 0.4 to 8.3 ppb (average, 2.7 ppb) when 
they are present at 100 ppm, and at 5-59 ppb when they are present at 
300 ppm. It was estimated that it would take longer than 18 h to 
reach a steady state and concluded that further study was needed to 
define the reaction kinetics. (See Chapter 5 for discussion of the 
potential for the formation of BCME in the atmosphere.) 

The carcinogenic potential of hexamethylenetetramine (HMT) , which 
can decompose in an acid medium to release formaldehyde and ammonia, 
has been examined. * 7 Mice and rats were given fresh solutions of 
HMT in drinking water every 24 h at 0.5-5% for 30-60 wk and at 1-5% 
for 2-104 wk, respectively. Mice were observed for up to 130 wk, and 
rats for up to 3 yr. At 5% HMT, there was 50% mortality in the rats 
after 2 wk. No significant effects on growth or survival were 
observed in any of the other groups of rats or in the mice. 
Histologic examination indicated that no effects were attributable to 
HMT. No carcinogenic activity was observed. 



EFFECTS IN HUMANS 

The principal effect of low concentrations of formaldehyde 
observed in humans is irritation of the eyes and mucous membranes. 
Table 7-2 summarizes data on human responses to airborne formaldehyde 
at various concentrations. It shows a wide range in formaldehyde 
concentrations reported to cause specific health effects. The 
severity of symptoms appears to be dose-related at extremes of 
concentration. In general, at low concentrations, below 0.05 ppm, no 
effects were reported. Objective changes in laboratory tests (i.e., 
optical chronaxy, EEC, etc.) without manifest symptoms were reported 
at concentrations beginning at 0.05 ppm, but more often at 1.5 ppm and 



186 

TABLE 7-2 
Reported Health Effects of Formaldehyde at Various Concentrations 



Approximate 
Formaldehyde 
Concentration, 
ppm 

U-0.5 
0.05-1.50 
0.05-1.0 



iealth Effects Reported 
None reported 
Neurophysiologic effects 
Ddor threshold 

Eye irritation 

Upper airway irritation 



Lower airway and pulmonary 
effects 



Pulmonary edema, inflam- 
mation, pneumonia 

Death 



0.01-2.0 a 



0.10-25 



5-30 



50-100 



100+ 



References 
65, 132, 
65, 132, 198 

15, 20, 65, 68, 
112, 175, 207, 215, 
217 

61, 78, 133, 137, 
163, 168, 175, 198, 
207, 217 

3, 9, 15, 20, 60, 

102, 107, 134, 137, 

173, 192, 198, 215, 
217, 218 

68, 71, 85, 86, 107, 
151, 152, 167, 173, 
198, 204, 215, 218 

16, 152, 218 
16, 152 



a The low concentration (0.01 ppm) was observed in the presence of other pollutant 
that may have been acting synergistically. 



187 

higher. The odor of formaldehyde is generally perceived by about 1 
ppm, but some people can detect 0.05 ppm. variable nonspecific 
complaints such as increased thirst, dizziness, headache, tiredness, 
and difficulty in sleeping are difficult to evaluate; however, they 
were generally reported when concentrations exceeded 1 ppm. Symptoms 
of eye irritation were reported at concentrations as low as 0.05 ppm. 
At concentrations at or above 1 ppm, nose, throat, and bronchial 
irritation was noted. Such irritation was readily reported when the 
concentration reached 5 ppm. When concentrations exceeded 50 ppm, 
severe pulmonary reactions occurred, including pneumonia, bronchial 
inflammation, and pulmonary edema, sometimes resulting in death. 

Table 7-2 clearly shows the variability and overlap of responses 
among subjects. Some persons develop tolerance to olfactory, ocular, 
or upper respiratory tract irritation. Such factors as smoking habits, 
socioeconomic status, preexisting disease, various host factors, and 
interactions with other pollutants and aerosols are expected to modify 
these responses. 



EYE 

Eye irritation is a common complaint of persons exposed to 
formaldehyde vapor. 133 16B 175 207 217 Formaldehyde is detectable at 
0.01 ppm, and at 0.05-0.5 ppm it produces a more definable sensation 
of eye irritation. 61 163 198 Occupational exposures at 0.9-1.6 ppm 
to formaldehyde released from paper pulp treated previously with 
urea-formaldehyde or melaraine- formaldehyde resulted in complaints of 
itching eyes, dry and sore throats, disturbed sleep, and unusual 
thirst on awaking in the morning. 137 Eye, nose, and throat 
irritation was reported by three of 16 subjects exposed for 5 h/d for 
4 d at 0.3 mg/m 3 (0.2 ppm) and 15 of 16 subjects exposed at 1.0 
mg/m 3 (0.7 ppm) in a chamber. 9 Sim and Pat tie 175 exposed 12 men 
in an exposure chamber at 13.8 ppm for 30 min. There was considerable 
nasal and eye irritation when the men first entered the chamber. 
However, the eye irritation was reportedly not severe, and the 
symptoms wore off after about 10 min in the chamber. Other studies 
reported that eye irritation may occur at concentrations below 1 
ppm. 133 lse 175 207 217 Marked irritation with watering of the eyes 
occurs at a concentration of 20 ppm in air. 198 Eye damage from 
formaldehyde vapor at low concentration is thought not to occur, 
because of the protective closure of the eye that results from 
discomfort. 78 Increased blink rates were noted at concentrations of 
0.3-0.5 ppm in persons studied in so-called pure air irradiated in 
smog chambers. 16B Blink rate, although used as an objective measure 
of eye irritation, appears variable for any given subject. The 
irritant effects of formaldehyde seem to be accentuated when it is 
mixed with other gases. In 14 smog-chamber tests, there was an 
average eye-irritation index of 4.9 1.0 units (on a scale of 0-24; 
0-16, none to severe irritation, and over 16, lacrimation in more tha 
50% of the subjects) . It was concluded that the human subjects teste> 
could readily detect and react to formaldehyde at as low as 0.01 ppm. 



188 

A difference in the concentration-response curves for formaldehyde was 
seen in the presence of photooxidation products of ethylene and 
propylene. A linear relationship was noted between eye irritation and 
formaldehyde concentration over a range of 0.3-1 ppm. It seemed that 
formaldehyde and peroxyacetylnitrate accounted for 80% and 20%, 
respectively, of the eye irritation associated with photochemical air 
pollution. In the usual smog-chamber experiments, dilute mixtures of 
nitric oxide, nitrogen dioxide, and hydrocarbons in air are 
irradiated. The Committee is not certain about the extent to which 
nitric acid, formic acid, and similar compounds shown to be present 
since the earlier studies were done contributed to the eye irritation 
observed in those experiments. 

Accidental splash exposures of human eyes to aqueous solutions of 
formaldehyde have resulted in a wide variety of injuries, depending on 
concentration and treatment. These range from discomfort and minor 
transient injury to delayed but permanent corneal opacity and loss of 
vision. Immediate flushing with water spared the eyes of one worker 
who received a splash injury from 40% formaldehyde solution. 100 A 
similarly exposed coworker whose eyes were not flushed with water lost 
vision in both eyes. Results of other accidental exposures to aqueous 
formaldehyde in humans and experimental ocular studies in animals were 
described by Grant. 78 Potts has shown that intravenous 
administration of formaldehyde (at 0.9 g/kg) has a pronounced action 
on retinal function, as indicated by changes in alpha and beta waves 
of the electroretinogram that were correlated with ophthalmoscopic 
retinal edema. l53 The changes would be missed if histology alone 
were used to detect them. In a NIOSH study, a complete visual test 
battery and ophthalmologic examination of workers exposed at 1.5 ppm 
revealed no effects of formaldehyde on the eye. 210 

In summary, human eyes are very sensitive to formaldehyde, 
detecting atmospheric concentrations of 0.01 ppm in some cases (when 
mixed with other pollutants) and producing a sensation of irritation 
at 0.05-0.5 ppm. Lacrimation is produced at 20 ppm, but damage is 
prevented by closure of the eyes in response to discomfort. Aqueous 
solutions of formaldehyde accidentally splashed into the eyes must be 
immediately flushed with water to prevent serious injury, such as lid 
and conjunctival edema, corneal opacity, and loss of vision. Table 
7-3 summarizes some of the studies concerning eye irritation. 



OLFACTORY SYSTEM 

The odor threshold of formaldehyde is usually around 1 ppm, but 
may be as low as 0.05 ppm. 15 20 65 ^2 173 i?s 207 217 olfactory 
fatigue with increased olfactory thresholds of rosemary, thymol, 
camphor, and tar was reported among plywood and particleboard workers 
and is presumed to be associated with formaldehyde exposure. 215 



189 



TABLE 7-3 
Eye Irritation Effects of Formaldehyde 



Formaldehyde 

Concentration, 

ppm 



0.03-3.2 

13.8 
20 

0.25 
0.42 

0.83-1.6 



4-5 

0.9-2.7 
0.3-2.7 
0.9-1.6 

0.13-0.45 

0.067-4.82 
0.02-4.15 
0.03-2.5 



Exposure 
Chamber single : 

20-35 min; gradually 
increasing concentra- 
tion 

30 min 

Less than 1 min 

Chamber repeated : 
5 h/d for 4 d 
5 h/d for 4 d 

5 h/d for 4 d 
Occupational : 



Indoor residential: 



Effects on Eyes Refer 



Increase in blink rate; 21 
irritation 



Irritation (and nose 17 
irritation) 

Discomfort and lacrima- 1 
tion 



19% "slight discomfort" 

31% "slight discomfort" 
and conjunctival irrita- 
tion 

94% "slight discomfort" 
and conjunctival irrita- 
tion 



Irritation, lacrimation, 
and discomfort in 30 min 

Tearing 

Prickling and tearing 1 

Intense irritation and 1 
itching 

Stinging and burning 2 



Tearing 

Irritation 

Irritation 



190 
RESPIRATORY TRACT 

The human nose adjusts the temperature and water-vapor content of 
air and removes a large proportion of foreign gases and dusts, * 5 ** 
and the nasal mucociliary system clears foreign material deposited on 
it. Nasal congestion from injury may lead to partial mouth-breathing; 
when nasal functions are impaired or the nose is otherwise bypassed 
for mouth-breathing, the burden of conditioning and cleaning the air 
falls on the lung. If the nasal defense system is disturbed or if 
mouth-breathing occurs, greater concentrations of formaldehyde will 
reach the lungs, and other noxious materials that are ordinarily 
cleared from the airways may be retained. In this regard, the 
differences in breathing of rats and mice should be noted. Rats and 
mice are obligatory nose breathers; therefore, nasal defense 
mechanisms may be more important in these animals. Thus, with respect 
to target organs for formaldehyde, it may be inappropriate to 
extrapolate results of rat and mouse formaldehyde-inhalation 
experiments directly to humans. 



Upper Airway Irritation 

Symptoms of upper airway irritation include the feeling of a dry 
throat, tingling sensation of the nose, and sore throat, usually 
associated with tearing and pain in the eyes. Irritation occurs over 
a wide range of concentrations, usually beginning at approximately 0.1 
ppm, but reported more frequently at 1-11 ppm 15 20 60 102 107 137 215 217 
(see Table 7-2) . Tolerance to eye and upper airway irritation may 
occur after 1-2 h of exposure. 15 102 173 However, even if tolerance 
develops, the irritation symptoms can return after a 1- to 2-h 
interruption of exposure. 3 1S 102 191 * 173 192 As in the case of eye 
irritation, some persons seem to tolerate higher concentrations, 16-30 
ppm perhaps subjects who developed tolerance. 

When 16 healthy young subjects were exposed to formaldehyde at 
0.25, 0.42, 0.83, or 1.6 ppm for 5 h/d for 4 d, nasal-mucus flow rate 
was decreased at all concentrations except 0.83 ppm. 9 Subjective 
responses to formaldehyde included slight conjunctival irritation and 
dryness of the throat and the upper third of the nose. 

Helwig reported that schoolchildren and teachers developed eye and 
respiratory tract irritation, gastrointestinal disturbances, increased 
thirst, and apathy after moving into a prefabricated school 
building. 81 * The "new-building odor" was particularly strong after 
weekends and holidays. Measurements of airborne formaldehyde made 
with Drager tubes revealed concentrations of 5 ppm or more on one 
occasion. Mild dysrhythmias were present in 20 children who underwent 
EEC studies. No details were given regarding the medical complaints 
or the number of children who developed adverse reactions while 
attending classes. The author felt that plastic polymers used in 
chipboard might also produce similar effects. Children who moved to 
another building after graduation no longer had any symptoms. 

Eye and upper respiratory tract irritation were noted in some 
employees of funeral homes that used formaldehyde and paraformaldehyde 



191 

in the embalming process; airborne concentrations in the embalming 
rooms were 0.25-1.39 ppm. ^2 & garment factory had airborne 
concentrations of 0.9-2.7 ppm; 15 eye and upper respiratory tract 
irritation were more common in areas where large quantities of 
partially completed permanent-press materials accumulated. 

The incidence of chronic rhinitis and pharyngitis was higher among 
formaldehyde-exposed workers in a wood-processing facility than in a 
control group. 198 218 A majority of workers complained of throat 
irritation, diminished smell, and dryness of the nose and pharynx. 
Examination of the nose and throat revealed hypertrophic or subtrophic 
nasal mucosa and subtrophic or atrophic pharyngitis in almost half th 
exposed workers. The incidence of pathology was highest in workers 
with the most exposure to formaldehyde. Formaldehyde concentrations 
reportedly ranged from 0.5 to 8.9 ppm, although occasional brief 
excursions above this limit were also observed. This study of 
wood-processing employees did not include measurements of other 
airborne contamintants, such as wood dust. In another study, reduced 
mucociliary function of the nasal mucosa and increased olfactory 
threshold to rosemary, thymol, camphor, and tar were observed in 
formaldehyde-exposed workers, compared with controls, regardless of 
evidence of nasal pathology. 215 

Nasal cancers in humans have been reported in some highly select 
occupations, such as wood-working and work with nickel. 1 199 
Because of the shape of and the high linear velocity of air in the 
anterior part of the nose, a large portion of dust that enters the 
nose is deposited in this portion. But the main nasal passage has a 
large surface area and is narrow, and air in this portion has low 
linear velocity; gases are therefore absorbed here. There maybe a 
direct or indirect local effect of chemical agents or an inter ferenc. 
with repair mechanisms at the sites of deposit or absorption. Furth. 
research is necessary concerning the morphology of the nasal 
turbinates and the histopathology of the nasal mucosa in rats, mice, 
and humans before definitive comparisons can be made with respect to 
exposure to specific chemicals, such as formaldehyde. 

in summary, irritation of the nose and throat caused by 
formaldehyde may occur at concentrations of Q '\**l' b ^ 
frpmientlv at 1-11 ppm. Examinations of the nose and throat 
cnronfc changes thafare .ore severe In persons PJ 
concentrations. Exposure to formaldehyde can cause alterations in 

for animal carcinogenicity is discussed elsewhere in this report. 

Lower Airway and pulmonary Effects 

Lower airway irritation that is characterized clinically by cou 
ches^ghtness! and whee^ , .reported * * pe^le exposed^ 

Perslnf apprenticed to ^aldehyde at high concentrations a 



192 

usually normal, except for occasional reports of accentuated 
bronchovascular markings, but pulmonary- function test results may be 
abnormal. 218 Acute respiratory distress was reported in a physician 
after several hours of formaldehyde exposure. 152 Physical 
examination of the physician's chest revealed diffuse rales and 
occasional rhonchi. A chest x ray was interpreted as showing early 
pulmonary edema. It is not known whether this case constitutes an 
example of a hypersensitivity reaction to formaldehyde or acute 
chemical pneumonitis. No specific information was given on the 
exposure to formaldehyde. 

Pulmonary-function studies of rubber workers exposed to a 
hexamethylene-tetramine-resorcinol resin showed decreased pulmonary 
function. 71 However, no association could be demonstrated between 
concentrations of airborne resorcinol, formaldehyde, hydrogen cyanide, 
or ammonia and change in pulmonary function. In a study of employees 
who manufacture filters with fibers that are impregnated with 
phenol-formaldehyde, a reduction in the ratio of FEVi to F7C, 
expressed as percent, and maximal expiratory flow at 50% of vital 
capacity were noted on Monday morning, compared with values of the 
previous Friday, for employees who had worked more than 5 yr. 167 
Detailed measurements of formaldehyde were not made, but two surveys 
reported concentrations of 0.4-0.8 ppm and 9.14 ppm. The work 
environment included other pulmonary irritants, such as phenol and 
acrylic fiber breakdown products. Chronic cough and sputum production 
occurred more often in those currently employed in production for over 
5 yr than in those never involved in production, although little 
change in pulmonary-function test results was noted during the course 
of a workweek or workday. 

The prevalence of respiratory illness and complaints among 
employees in eight textile plants was more than 15% for four plants 
and 5-15% for the other four. 173 These results were obtained from 
medical records and were not confirmed through medical examination of 
the employees. Airborne formaldehyde concentrations were 0-2.7 ppm, 
with an average of 0.68 ppm. Workers reported that formaldehyde 
concentrations varied considerably with changes in temperature and 
humidity. It is not known whether the airborne formaldehyde 
concentrations were representative of seasonal fluctuations. 

Pulmonary edema, pneumonitis, and death could result from very 
high formaldehyde concentrations, 50-100 ppm. 16 152 21B It is not 
known what concentrations are lethal to humans, but concentrations 
exceeding 100 ppm would probably be extremely hazardous to most and 
might be fatal in sensitive persons. 



Asthma 

Allergic contact dermatitis caused by formaldehyde sensitivity is 
well-recognized, but there have been relatively few documented cases 
of occupational asthma attributable to formaldehyde and proved by 
bronchial inhalation challenge tests. 85 86 110 1! 3 ^ lsl 16I 167 
is* 20* In t he cases reported by Hendrick and Lane, nurses in a 



193 

renal hemodialysis unit developed asthma as a result of continued 
exposure to formaldehyde that was used to sterilize the 
artificial-kidney machines. 85 8S In all, eight of 28 persons 
studied had experienced asthmatic attacks or bronchitis. In five of 
the eight, attacks had been recurrent for at least 3 yr, and only on 
had ever experienced such symptoms before joining the unit. Bronchi 
provocation tests were positive in only two persons. In those two, 
wheezing began approximately 2-3 h after exposure, and the results c 
measured pulmonary function tests fell by as much as 50%. Reactions 
persisted for from 10 h to 10 d, depending on the exposure; 
concentrations in the air were not reported. The asthmatic reactior 
could be inhibited by beclomethasone aerosol. ' 



Mechanism of Airway Responses to Formaldehyde 

Formaldehyde has been shown to cause bronchial asthma in 
humans . 8 s a e no 113 i a i s i i e * i e 7 1 9 n 2 o H Although asthmatic 
attacks are in some cases due specifically to formaldehyde 
sensitization or allergy, formaldehyde seems to act more commonly a 
direct airway irritant in persons who have bronchial asthmatic atta 
from other causes. Persons with bronchial asthma respond to numero 
agents, such as exogenous irritants and allergens, respiratory 
infections, cold air, smoke, dust, and stress. 22 7 "* The asthmatic 
person seems to represent an extreme on the scale of respiratory 
sensitivity to inhaled irritants. The data suggest a dose-response 
relationship, with increasing numbers of asthmatics having attacks 
air pollution worsens. Thus, the airways of asthmatics respond to 
many nonspecific inhaled irritants, including formaldehyde. 

The exact mechanism of the asthma syndrome related to formaldel 
exposure is not known. It has been suggested that an immunologic 
basis is sometimes operative. However, no studies have demonstrate 
the presence of specific circulating immunoglobulins (IgE or IgG) 
affected persons. 

Non immunologic mechanisms may explain the effects of formaldeh 
on the airways. Although formaldehyde at low concentrations may c 
asthmatic symptoms in some sensitized subjects, in irritant 
concentrations it produces bronchoconstriction in even normal 
persons. The effect of lower concentrations on airways may be sin 
to those of chemicals, such as toluene diisocyanate (TDI) , that at 
concentrations not ordinarily considered irritating do produce an 
adverse airway response unrelated to allergy, possibly on a 
pharmacologic basis. 27 28 1SO l76 213 An abnormality of the 
beta-adrenergic receptor system has been proposed as an explanati< 
for asthma due to TDI. 27 2a Other possible pharmacologic mechanii 
may be similar to those associated with cotton dust, cotton extra* 
have been reported to cause histamine release from basophils. 19 

Inhalation of formaldehyde vapors may itself act directly on 
smooth muscle or nerve endings, causing airway hyperreactivity, a 
important component of bronchial asthma. ^ ll1 ll 9 182 Methachol 



194 

and histamine challenge tests have demonstrated this hyperreactivity 
with other environmental pollutants. 21 22 26 28 7>t 

Recently, alterations in the bronchial mucosal epithelial barrier 
have been proposed as a theory to explain the effects of environmental 
agents on airways. 18 88 Normally, the bronchial mucosa provides a 
barrier, preventing entry of high-molecular-weight protein into the 
submucosal layer . Environmental agents can increase both the 
permeability of the bronchial epithelium and the response to histamine 
at subthreshold concentrations. The disruption of the bronchial 
epithelial barrier, perhaps the tight junction between cells, permits 
the environmental and pharmacologic agents better access to the 
underlying tissue and the capability of reaching afferent nerve fibers 
that are directly beneath the tight junctions of the epithelial 
cells. This greater accessibility to the nerve fibers leads to the 
apparent fncreased reactivity of airways. In addition, formaldehyde 
may be able to act directly on bronchial smooth muscle beneath the 
epithelial barrier. 101 Nonspecific mast-cell degranulation from 
formaldehyde, resulting in release of vasoactive substances and 
causing smooth-muscle contraction, is another possible nonimmunologic 
mechanism. 



Summary 

A number of lower airway and pulmonary effects may occur from 
formaldehyde exposure. In most normal persons exposed to 
formaldehyde, concentrations greater than 5 ppm will cause cough and 
possibly a feeling of chest tightness. It is possible that normal 
persons will experience these symptoms at 2-3 ppm, but data are not 
available on this. In some susceptible persons, concentrations below 
5 ppm can cause these symptoms, including wheezing. In persons with 
Bronchial asthma, the irritation caused by formaldehyde may 
precipitate an acute asthmatic attack, possibly at concentrations 
Delow 5 ppm. Rarely does a person with asthma become sensitized 
(allergic) specifically to formaldehyde and thereby respond to 
concentrations lower than 0.25 ppm. This reaction is not due to 
formaldehyde's irritant properties, but is related to some poorly 
mderstood immunologic (or possibly nonimmunologic) mechanism. In 
concentrations greater than 50 ppm, severe lower respiratory tract 
iffects can occur, with involvement not only of the airways, but also 
>f alveolar tissue. Acute injury of this type includes pneumonia and 
Loncardiac pulmonary edema. 



'.KIN 

Skin contact with formaldehyde has been reported to cause a 
ariety of cutaneous problems in humans, including irritation, 
llergic contact dermatitis, and urticaria. 1 ** 162 18 Allergic 
ontact dermatitis from formaldehyde is relatively common, and 
ormaldehyde is one of the more frequent causes of this condition both 



195 

in the United States* 6 and in other areas.es The North American 
Contact Dermatitis Group reported that formaldehyde is the tenth 
leading cause of skin reactions among dermatitis patients patch-tested 
for allergic contact dermatitis. Approximately 4% of 1,200 patients 
had positive skin reactions when tested with 2% formalin (0.8% 
formaldehyde) under an occlusive patch."* Minor epidemics of 
allergic contact dermatitis have been described in diverse situations, 
for example, among nurses who handled thermometers that had been 
immersed in a 10% solution of formaldehyde 161 and among those who 
were exposed to formaldehyde in hemodialysis units. 180 

In many cases, either the initiation or the elicitation of the 
allergy has been caused by contact with formaldehyde or formalin, but 
it may also result from formaldehyde-releasing agents used in 
cosmetics, medications, and germicides, from incompletely cured 
resins, and from the decomposition of formaldehyde-containing resins 
used in textiles. 115 People with cutaneous allergy to formaldehyde 
have particular problems because there are so many sources of 
formaldehyde exposure in ordinary daily life. For example, the FDA 
lists 846 cosmetic formulations containing formaldehyde. 201 The 
skin reaction rate from cosmetic formulations containing formaldehyde 
has not been excessive, because it is used mainly as a preservative- in 
shampoos, whose contact time with skin is short. Formaldehyde- 
releasing cosmetic preservatives, such as Quaternium-15, have shown a 
greater reaction frequency than formaldehyde itself (unpublished data 
from Cosmetics Technology Division, Bureau of Foods, FDA). 

Humans can come into contact with low concentrations of 
formaldehyde from many sources, and repeated contact with them may be 
sufficient to provoke responses in people with allergic contact 
sensitization. It is important to mention that previously "normal" 
people can become sensitized. These sources include components of 
plastics, glues, antifungal disinfectants, preservatives, paper, 
fabrics, leather, coal and wood smoke, fixatives for histology, and 
photographic materials. 70 Available data do not permit the 
determination of a degree of exposure to formaldehyde-containing 
products that would be safe once sensitization has occurred. 

Occupational dermatitis from urea- formaldehyde dusts and powders 
(containing free formaldehyde) in the workplace was reported by 
Harris. 81 Exposed skin e.g., on the face, lips, and neck and in 
interdigital areas was affected, as well as such permeable skin sites 
as the scrotum and eyelids and intertriginous areas, such as the 
armpit and flexure areas of the arms. 

The response of formaldehyde-sensitive persons is related to the 
extent of exposure (see Table 7-4). 126 However, most sensitized 
persons can tolerate topical axillary products containing formaldehyde 
at up to about 30 ppm. 96 With increasing concentration, one sees a 
higher frequency of responders, l 27 probably because skin penetration 
by formaldehyde varies from one person to another and even from one 
site to another on the same person. Thus, different amounts of 
formaldehyde may reach different target sites. The dose needed to 
elicit a response depends on these factors and others, such as 
occlusion, temperature, contact time, and vehicle. 



196 



TABLE 7-4 

Elicitation (Occluded) of Skin Reactions in 
Five Formaldehyde-Sensitized Subjects 8 

Formaldehyde 

Challenge No. 

Concentration, Responding 

% (n => 5) 

1 4 

0.5 2 

0.2 1 

0.1 1 

0.01 1 

I tyc. 

a Data from Marzulli and Maibach. 



197 

Allergic contact dermatitis is a manifestation of cell-mediated 
immunity. The standard diagnostic test for this condition is the 
epidermal patch test, in the case of formaldehyde, interpretation may 
be complicated by the irritant potential of the substance. Patch 
testing is now generally conducted with a 2% concentration of 
formalin. Before the early*1970s, a 5% solution in water was commonly 
used; many of the reported results of earlier patch testing may have 
been spurious. ** Patch testing for skin sensitization to 
formaldehyde resin is performed with a 5-10% concentration of the 
resin in petrolatum. 2 

So-called predictive tests for skin sensitization are used first 
on animals, then on man to identify the allergenic potential of new 
substances or formulations entering the marketplace. Guinea pigs are 
the favored animal species. The Draize intraderraal technique* 9 and 
one of the published adjuvant techniques 125 are animal methods often 
used before human investigation in evaluating skin hypersensitivity. 
The Draize technique is likely to underestimate the human response, 
whereas adjuvant (Freund's complete adjuvant) techniques are likely t 
overestimate it. In human predictive testing, two techniques are 
useful: the "modified Draize" 127 and the "maximization" 1011 
methods. Results obtained for formaldehyde with some of these 
techniques are compared in Table 7-5. 

Although formaldehyde has been reported to cause contact 
urticaria, it is not yet clear whether this is immunologically 
mediated. ^^ Formaldehyde is a potent sensitizer and irritant, 
repeated exposure to it may also result in dermatitis. 

In summary, formaldehyde is a skin irritant and skin sensitizer. 
Formaldehyde plastics sensitize skin by contact with formaldehyde 
resin or by releasing formaldehyde from incompletely cured plastic 
dusts or particles. Aqueous formaldehyde solutions (e.g., cosmetic 
formulations) elicit a skin response (under occlusive cover) in some 
sensitized people at concentrations as low as 0.01%, but underarm 
products containing up to 0.003% formaldehyde are tolerated by most 
sensitized persons. Formaldehyde-releasing preservatives, such as 
Quaternium-15 , may sensitize to formaldehyde or to the parent 
material. Occupational exposure to free formaldehyde in 
urea-formaldehyde dusts and powders may also result in dermatitis. 



CENTRAL NERVOUS SYSTEM 

Central nervous system responses to formaldehyde have been teste 
in a variety of ways, including by determination of optical 
chronaxy,i32 electroencephalographically, 6S and by the sensitivity 
of the dark-adapted eyes to light. 132 Responses are reported in 
some persons at 0.05 ppm and are maximal at about 1.5 ppm. 
Formaldehyde at less than 0.05 ppm probably has little or no objectj 
adverse effect. 198 Fel'dman and Bonashevskaya reported that 
formaldehyde at 0.032 ppm produced no electroencephalographic change 
and did not reach the odor threshold in five extremely sensitive 



198 



TABLE 7-5 

Predictive Skin-Sensitization Test Results with 
Aqueous Formaldehyde 



Positive-Response 
Species Method Frequency, % 

119 
Guinea pig Draize intradermal 5 

Adjuvant (maximization) 80 119 

Human Maximization 72 119 

Modified Draize 4.5-7.8 127 



199 



subjects. 65 Melekhina demonstrated sensitivity of the dark-adapted 
eye to light at about 0.08 ppm. 132 



ALIMENTARY TRACT 

Ingestion of formaldehyde has been reported to cause headache, 
upper gastrointestinal pain, 23 51 57 105 122 a allergic 
reactions, 19 * corrosive effects on gastrointestinal and respiratory 
tracts, 57 is lllt and systemic damage. 57 105 ll * Accidental or 
suicidal poisoning with formaldehyde usually involves the ingestion 
aqueous solutions; death occurs after the swallowing of as little as 
30 ml of formalin. 16 105 Gastrointestinal tract damage is most 
marked in the stomach and lower esophagus, with the tongue, oral 
cavity, and pharynx generally not severely affected. 198 The small 
intestine may occasionally be involved; perforated appendix is a ra 
complication. When the chemical infiltrates around the epiglottis, 
injury to the larynx and trachea may occur. 16 105 19B After 
ingestion, there may be loss of consciousness, vascular collapse, 
pneumonia, hemorrhagic nephritis, and spontaneous abortion. 16 10S 
One autopsy report of a fatal ingestion described hardening of orga 
adjacent to the stomach (lung, liver, spleen, and pancreas), hypere 
and edema of the lungs, bilateral diffuse bronchopneumonia, fatty 
degeneration of the liver with subcapsular hemorrhage, renal tubula 
necrosis, and involvement of the brain. 16 10S 157 

Other avenues of acute poisoning include intravesical instillal 
of formalin for control of intractable bladder hemorrhage 36 and 
accidental irrigation of the colon with aqueous formaldehyde. 91 * 
Paresthesia, soft-tissue necrosis, and sequestration of bone have 
occurred when formaldehyde preparations have been used for 
devitalizing dental pulps. 79 8S 13S An outbreak of hemolytic anem 
among patients at a hemodialysis unit was traced to formaldehyde 
leaking from water filters impregnated with a melamine-formaldehyd 
resin. 1!t s 



EFFECTS ON REPRODUCTIVE SYSTEM 

Menstrual abnormalities and complications of pregnancy were 
reported to occur more frequently in Russian women employed in th 
textile industry and in contact with urea-formaldehyde resins. 171 * 
The unique role, if any, of formaldehyde in this study is not cle< 
because of the lack of information, e.g., on other potentially toa 
compounds in the workplace that might adversely affect the 
reproductive system, on the composition and comparability of the 
populations that were the source of the reported data, and on var 
demographic, socioeconomic, and physiologic factors. Never theles, 
is pertinent to summarize what was reported. Formaldehyde 
concentrations were 1.5-4.5 yg/m 3 for high-exposure trimmers, 
0.3-0.7 yg/m 3 for sorters, and 0.05-0.1 yg/m for others. 
About 70% of the women were under 40 yr old. Menstrual disorders 



200 

encountered more often in women with greater exposures (trimmers) and 
in direct relationship to duration of employment. Oligodysmenorrhea 
was the major menstrual disorder: 24.3 2.2% of the trimmers, 20.2 
2.2% of the sorters, and 9.2 1.1% of the controls. 
Complications of pregnancy were more prevalent in the more exposed 
group. Anemia, as a complication, was noted twice as often in the 
exposed group. Other complications such as intrauterine asphyxia, 
premature rupture of the membranes, late toxemia, threatened abortion, 
and premature deliveries were analyzed and said to be more frequent 
in the exposed groups, but no substantial analysis was reported. 
There was also a greater percentage of newborns with low birthweight 
in the exposed groups. Of the infants born to women who had contact 
with formaldehyde, 26.9 4.9% weighed 2,500-2,990 g at birth, 
compared with 11.3 1.3% of the infants born to women in the 
control grup ( < 0.05) . 



BLOOD 

Hemolysis has been observed among patients undergoing chronic 
hemodialysis . It resulted in contamination of several lots of 
dialysis water with an excess formaldehyde concentration of 10 
mmol/L. 1 * 5 Water filters treated with melamine-formaldehyde resin 
were the source of the contaminated formaldehyde. A concentration as 
low as 0.1 mM caused decreased ATP content when incubated with blood 
cells. There is also evidence that formaldehyde sterilization of 
dialyzers may cause antibody-mediated hemolysis that contributes to 
renally induced anemia. 62 



CONSUMER COMPLAINTS IN RESIDENTIAL ENVIRONMENTS 

Over the last several years, increasing numbers of complaints have 
caused concern about the health hazards of residing in homes where 
formaldehyde is released into the living space. The Consumer Product 
Safety Commission (CPSC) received more than 1,000 complaints from 
users of mobile homes and conventional homes insulated with UF foam by 
March 1980. * 3 l * * 19S 197 The Department of Housing and urban 
Development reported an increase in complaints about formaldehyde 
during this same period. On August 1, 1979, the CPSC issued a 
consumer advisory on UF insulation, citing possible health problems 
associated with this type of insulation. 131 * 19S 

A number of studies have been undertaken to determine the 
magnitude and extent of formaldehyde exposure of persons in the 
residential environment. 3 2 * 30 ? 7 87 i** ^z iss 211 In 1975, 
Anderson et^al. 10 reported formaldehyde concentrations ranging from 
0.08 to 2.24 mg/m 3 , with an average of 0.62 mg/m 3 , in 25 rooms in 
23 conventional Danish homes with chipboard in their interior 
construction, in 1977, Breysse reported four cases (investigated 
in 1961) in which people in conventional buildings had complained of 
eye and upper respiratory irritation in association with exposure to 



201 

formaldehyde from particleboard and chipboard. In a compilation of 
periodic investigations (1968-1977) of complaints, he noted 74 raobilt 
homes, six of which were unoccupied, in which 92 persons experienced 
adverse reactions "allegedly" resulting from exposure to formaldehyde 
The range of concentrations reported was 0-2.5 ppm; fewer than 10% 
were above 1.0 ppm. The prevalence of symptoms in the 92 people was 
reported as follows: eye irritation, 80 persons; nose irritation, i: 
respiratory tract irritation, 58; headache, 51; nausea, 12; and 
drowsiness, 26. Severity of symptoms was not correlated with 
formaldehyde concentration. However, it should be pointed out that 
people questioned noted relief of symptoms when they left their home, 
for the weekend and return of symptoms when they went home. 

In November 1977, the Connecticut Department of Health and 
Consumer Protection began receiving complaints from state residents 
who had UF foam insulation installed in their homes. 77 By September 
1978, 84 complaints had been received. The Department tested the 84 
homes and found formaldehyde in the air in 75. The sensitivity of t 
testing system was reported to be less than 0.05 ppm. Health symptom 
were reported by 224 residents of 74 homes, in which detectable 
concentrations of formaldehyde ranged between 0.5 and 10 ppm, with a 
mean of 1.8 ppm. The symptoms of the residents included eye, nose, 
and throat irritation; GI tract symptoms; headache; skin problems; s 
some miscellaneous complaints, such as fatigue, aches, and swollen 
glands. In 37%, however, symptoms occurred when formaldehyde was nc 
detectable by the methods used. When formaldehyde was detectable 
(0.5-10 ppm), 49% of the occupants had eye irritation, 37% nose and 
throat irritation, 46% headache, and 22% GI tract symptoms; in homes 
with no detectable formaldehyde, 26% had eye symptoms, 41% nose and 
throat irritation, 26% headache, and 42% GI tract symptoms. 

Since January 1978, the Wisconsin Division of Health has collet 
air samples and environmental data on 100 mobile homes, conventiona 
homes, and offices that have particleboard in their construction am 
foam insulation. 46 Air samples were collected in midget impingers 
and analyzed with the chromotropic acid procedure. Health informat 
was obtained from the occupants of these structures. Formaldehyde 
ranged from undetectable to 4.18 ppm. The median concentration was 
0.35 ppm (0.47 ppm for mobile homes and 0.10 ppm for conventional 
homes) . The symptoms observed included eye and upper respiratory 
tract irritation, headache, fatigue, nausea, vomiting, diarrhea, an 
respiratory problems. As formaldehyde concentrations increased, th 
percentage of persons experiencing eye irritation increased frm 60% 
92%. Among infants and young children, vomiting, diarrhea, and 
respiratory problems were identified as particularly important 
conditions. The relationship between smoking and formaldehyde 
concentration in the dwelling was examined; smoking did not 
significantly increase formaldehyde concentration in the home at tl 
time of concentration measurement. 

Consumer reports have also been summarized by the CPSC. 196 
In-depth investigations of 15 persons were conducted by the CPSC f: 
staff and by private contractors. Most of the reported symptoms w 
related to eye and throat irritation. Five persons were admitted 1 



202 

the hospital for medical problems attributed to formaldehyde. The 
CPSC also collected more than 100 reports from newspaper clippings, 
consumer complaints, and state reports that were not investigated in 
detail. 



NONSPECIFIC SUBJECTIVE SYMPTOMS IN EXPOSED POPULATIONS AND EFFECTS ON 
INFANTS AND CHILDREN 

Various subjective and nonspecific complaints have consistently 
been reported, including disturbed sleep, thirst, headache, and 
nausea. 20 2<l sa fll 8lf 92 137 17S 19 19e 212 21S 

Recently, there has been concern about the effects of formaldehyde 
on infants and children. 21 * 1 The Wisconsin Division of Health 
conducted a survey between January 1, 1978, and November 1, 1979, that 
consisted of analysis of information collected with a questionnaire 
completed by 249 persons, representing 96 homes and 260 occupants. 
Two frequent findings were "nosebleed" and "rash" in infants and young 
children. Nine of 23 infants (less than a year old) required 
hospitalization; four were hospitalized for vomiting, diarrhea, or 
both and five for respiratory problems. Three of the latter five also 
had vomiting, diarrhea, or both. The mean formaldehyde concentration 
in the homes of the hospitalized infants was 0.68 0.66 ppm. In 
each case, symptoms reportedly disappeared when the infant was removed 
from the home and returned when the infant went home. 



OCCUPATIONAL STANDARDS FOR FORMALDEHYDE 

Occupational exposure limits issued by various countries are 
listed in Table 7-6. The present OSHA standard for formaldehyde is 3 
ppm, as a time-weighted average concentration over an 8-h workshift. 
In 1974, the ACGIH recommended a ceiling limit of 2 ppm, mainly 
because irritation might occur above this concentration. NIOSH has 
recommended a workplace ceiling limit of 1 ppm. 19e 



RESIDENTIAL STANDARDS FOR FORMALDEHYDE 

Occupational standards for formaldehyde have been determined in 
the United States and other countries, but the recommendations are for 
maximal time-weighted 8-h average concentrations for the workplace and 
for ceiling or peak concentrations. In the United States, there is no 
standard for formaldehyde for 24-h continuous nonoccupational 
exposure, as in the home. The American Industrial Hygiene Association 
has recommended an outdoor ambient-air standard of 0.10 ppm. 7 A 
panel of the National Research Council has stated that airborne 
formaldehyde in spacecraft for manned space flights should not exceed 
0.10 ppm for an exposure of 90 d to 6 mo. " The American Society 
of Heating, Refrigerating and Air-Conditioning Engineers has 
recommended 0.20 ppm as a 24-h residential exposure limit.' West 



203 

TABLE 7-6 
Occupational Standards for Formaldehyde in Effect, 1976 a 



Country 
United States: 



Standard 
mg/m j ppm 



Type 



Federal Standard 





3 


TWA 







5 


Ceiling 







10 


30-min ceiling 


AOGIH TLV 


2.5 


2 


Ceiling 


ANSI Z-37 





3 


TWA 







5 


Ceiling 







10 


30-min ceiling 


Florida 





5 


Ceiling 


Hawaii 





10 


Ceiling 


Massachusetts 





3 


Ceiling 


Mississippi 





5 


Ceiling 


Pennsylvania 





5 


TWA 







5 


5-min ceiling 


South Carolina 


___ 


5 


Celling 


Bulgaria 


5 





Ceiling 


Czechoslovakia 


2 





Ceiling 




5 





Peak 


Federal Republic of Germany 


b 


5 


Ceiling 


Finland 


6 


5 


Ceiling 


German Democratic Republic 


5 





Ceiling 


Great Britain 


12 


10 


Ceiling 


Hungary 


1 





Ceiling 


Italy 


5 





Ceiling 


Japan 


6 


5 


Ceiling 


Poland 


5 





Ceiling 


Rumania 


3 





Ceiling 


UAR 





20 


Ceiling 


USSR 


0.5 


0.4 


Ceiling 


Yugoslavia 


6 


5 


Ceiling 



Modified from NIOSH. 198 



204 

Germany, Denmark, and The Netherlands have residential standards of 
0.10, 0.12, and 0.10 ppm, respectively (C.D. Hollowell, personal 
communication; Hollowell et al.. 89 ). Sweden has recommended that a 
standard be set in the range of 0.10-0.70 ppm. 192 



SIGNIFICANCE OF ADVERSE HEALTH EFFECTS IN REGARD TO POPULATION AT RISK 

The total number of people who are exposed to formaldehyde and who 
manifest adverse health effects is difficult to determine. There is 
evidence that such responses may occur in a substantial proportion of 
the exposed population in the United States. The variability in 
response among exposed persons makes it particularly difficult to 
assess the problem. 

People are exposed to formaldehyde from occupational sources, 
consumer products, outdoor ambient air, and indoor air. 

In the occupational setting, about 1.4 million persons are 
directly or indirectly exposed to formaldehyde. It is not possible to 
determine exactly the exposure in each industry. However, owing to 
the irritant nature of formaldehyde, most workplaces probably have 
concentrations of less than 3 ppm more often around 1 ppm or less for 
an 8-h workday. 

Some 11 million persons live in homes that contain either UF foam 
insulation or particleboard made with UF resins. When measurements 
have been performed, a wide range of formaldehyde concentrations from 
0.01 ppm to 10.6 ppm, have been reported. Most homes have shown less 
than 0.5 ppm with a range of 0.1-0.2 ppm being more prevalent. 
Because people spend up to 70% of their time indoors, the exposure to 
formaldehyde released from UF foam or particleboard could be 
substantial. 

Formaldehyde concentrations measured in ambient air are lower than 
in the occupational or indoor residential situation. Outdoor 
concentrations vary, but are rarely more than 0.1 ppm and usually less 
than 0.05 ppm. However, the probability of high outdoor exposure to 
formaldehyde for the 220 million people in the United States does not 
appear to be substantial, except for unusual circumstances of traffic, 
fuel use, or automobile density. Consumer exposures are mainly by 
direct contact, and contact dermatitis is an important consideration, 
as has been discussed. 

Little is known about the magnitude of the population that is more 
susceptible to the effects of inhaling formaldehyde vapor. Asthmatics 
may constitute a segment of the general population that is more 
susceptible; inhalation even at low concentrations may precipitate 
acute symptoms. Airway hyperactivity may explain the susceptibility of 
asthmatics to formaldehyde at low concentrations. Using data gathered 
from over 1,500 methacholine challenge tests, one can estimate the 
prevalence of airway hyperreactivity in the population at large. 19 
About 9 million people in the United States have bronchial asthma. 
Essentially all will react positively to methacholine challenge tests 
and thus be considered to have hyper reactive airways. 190 The degree 
of airway reactivity is variable and depends on a number of 



205 

factors. 22 It has been estimated that 30% of atopic nonasthmatic 
people perhaps 10 million have positive methacholine tests. 190 
Townley e_t al^. reported that 5% of nona topic persons another 8.5 
million have positive methacholine tests. 190 Therefore, on the 
basis of calculations reported for positive methacholine challenge 
tests, it can be estimated that about 25 million persons in the United 
States, or 10-12% of the population, may be considered to have some 
degree of airway hyperreactivity. This population could potentially be 
more susceptible to formaldehyde. 

Information on other assumed susceptible populations is limited. 
The U.S. Department of Health, Education, and Welfare, in a 1977 
report on prevention, control, and elimination of respiratory disease, 
estimated that 10 million persons in the United States had chronic 
obstructive lung disease (excluding asthma). 200 A small percentage 
of them will have positive methacholine challenge tests. Britt et_ 
al_. 25 suggested that the presence of methacholine sensitivity and 
evidence of airway hyperreactivity are risk factors for the 
development of chronic obstructive pulmonary disease (COPD) . Perhaps 
patients with COPD who manifest airway hyperreactivity constitute a 
susceptible population, inasmuch as they react more acutely to 
airborne irritants, including formaldehyde. 

On the basis of sensitivity to methacholine, some atopic persons, 
some nonatopic subjects, and some COPD patients may constitute a 
potential formaldehyde-susceptible population. This population could 
also have greater eye and upper respiratory tract sensitivity. 
However, many apparently normal people react to the irritant 
properties of formaldehyde, and this makes it more difficult to 
determine the susceptible population. 

In another attempt to estimate the susceptible population 
(particularly in relation to eye, nose, and throat sensitivity) , 
information on a small number of healthy young adults exposed to 
formaldehyde at various concentrations for short periods was 
considered. 139 At 1.5-3.0 ppm, more than 30% of the subjects tested 
reported mild to moderate eye, nose, and throat (ENT) irritation 
symptoms, and 10-20% had strong reactions. When test subjects were 
exposed at 0.5-1.5 ppm, slight or mild ENT irritation was noted in 
more than 30%, but 10-20% still had more marked reactions. 
Approximately 20% of the subjects had slight ENT irritation in 
response to formaldehyde at 0.25-0.5 ppm. Finally, at the lowest 
concentration tested, less than 0.25 ppm, some exposed subjects ("less 
than 20 percent") still reported minimal to slight ENT discomfort. 
These data might be interpreted as suggesting that there are subjects, 
perhaps 10-20% of those tested, who are more responsive and may react 
acutely to formaldehyde at very low concentrations. 

Data on the proportion of the population susceptible to the 
irritant effects of formaldehyde seem to be consistent. The estimated 
prevalence of airway hyperreactivity (based on methacholine challenge 
testing) in the general population is 10-12% and about 10-20% of the 
subjects in the study just described showed excessive ENT 
sensitivity. We may get further information from mobile-home surveys 
from which environmental and clinical data are available. No 



206 

measurements of other airborne contaminants were made, so the 
importance of other substances in the household environment is not 
known. Irritation symptoms were reported by 30-50% of subjects when 
formaldehyde concentrations were greater than 0.5 ppm. When the 
concentration was less than 0.5 ppm, irritation symptoms were reported 
in fewer than 30% of subjects. Finally, in a more controlled study in 
which irritation symptoms were investigated, mild irritation responses 
(doubling of blinking rate) occurred in 11% subjects tested at 0.5 ppm, 

In summary, fewer than 20% but perhaps more than 10% of the 
general population may be susceptible to formaldehyde and may react 
acutely at very low concentrations, particularly if they are above 1.5 
ppm. People report mild ENT discomfort and other symptoms at less 
than 0.5 ppm, with some noting symptoms at as low as 0.25 ppm. 
Low-concentration formaldehyde exposures may produce ENT symptoms and 
possibly lower-airway complaints. In some susceptible persons, an 
"allergic" reaction to formaldehyde may occur at very low 
concentrations, causing bronchoconstriction and asthmatic symptoms. 
This particular type of reaction to formaldehyde appears to be 
uncommon; its exact prevalence cannot now be estimated. 



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161. Rostenberg, A., Jr., B. Bairstow, and T. W. Luther. A study of 
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162. Roth, W. G. Tylosic palmar and plantar eczema caused by 
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163. Rumack, B. Position Paper. Urea-Formaldehyde Foam. Denver: 
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165. Sasaki, Y., and R. Endo. Mutagenicity of aldehydes in 
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168. Schuck, E. A., E. R. Stephens, and J. T. Middleton. Eye 
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217 

170. Shapira, Y., A. Ben Zvi, and M. Statter. Folic acid 
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pp. 

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213:445-461, 1955. 



218 

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219 

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220 

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gases. Lav. Urn. 9:241-254, 1957. (in Italian; English summary) 



CHAPTER 8 
HEALTH EFFECTS OF SOME OTHER ALDEHYDES 



This chapter discusses the effects of aldehydes other than 
formaldehyde on biologic preparations/ animals, and man. It 
represents an extensive review of the available published information 
to assess the health effects of aldehydes on humans and animals. 



TOXICITY OF ALDEHYDES OTHER THAN FORMALDEHYDE 

The total of occupational exposures to aldehydes in 1976 is shown 
in Table 8-1. Direct evidence of the human health effects of 
aldehydes is related predominantly to eye irritation, olf action 
threshold, and irritation of the upper respiratory tract and skin. T 
a lesser degree, isolated human biochemical reactions have been 
monitored. 

Toxicity information obtained from animal studies for common 
aliphatic and aromatic aldehydes is summarized in Tables 8-2, 8-3, an 
8-4. The major pathophysiologic effects of aldehydes 31 are 
described briefly below. 



IRRITATION OF THE SKIN, EYES, AND RESPIRATORY MUCOSA 

Irritancy is a property of nearly all the aldehydes, but it occur 
more commonly and is more important in the case of those with lower 
molecular weights and those with unsaturation in the aliphatic chain 
or with halogenated substituents. The general and parenteral toxicit 
of these compounds appears to be related primarily to irritation, 
although in some cases (such as fluoroacetaldehyde or fluorobutanal) 
metabolic conversion to the corresponding fluorinated acids produces 
an extraordinarily high degree of toxicity. The irritant properties 
of the dialdehydes have not been extensively studied, but in some 
instances concentrated solutions can severely irritate the skin and 
the eyes. The acetals and the aromatic aldehydes in general have a 
lower degree of irritant action, although there are some exceptions. 
Furfural has irritant properties, but is not nearly as active as 
acrolein. 3 l 

221 



222 



TABLE 8-1 

Occupational Exposures to Aldehydes 3 

Aldehyde No. Exposures 

Acet aldehyde 1,744 

Acrolein 7,301 

Benzaldehyde 15,985 

n-Butyraldehyde 1,259 

Furfural 15,412 

Glutar aldehyde 35,083 

Glyoxal 3,848 

Propionaldehyde 1,544 

a Data from NIOSH. 111 



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226 

SENSITIZATION 

Direct sensitization to aldehyde vapors appears to be relatively 
rare, and sensitization to addition products, such as the bisulfites, 
almost never occurs. Because of the bifunctional nature of the 
dialdehydes, they should theoretically be capable of acting as skin 
sensitizers, but there have been few reports of this phenomenon. 31 

Sensitization to the unsaturated aldehydes may occur, but it is 
usually very difficult to separate the primary irritation from 
sensitization. Skin sensitization to the acetals and aromatic 
aldehydes appears to be infrequent. Pulmonary sensitization and 
asthma-like symptoms are rarely caused by the inhalation of 
aldehydes. 3 1 

ANESTHESIA 

Chloral hydrate and paraldehyde have unquestionable anesthetic 
properties. The former may act through its metabolism to 
trichloroethanol, and the latter by depolymerization to acetaldehyde. 
When administered experimentally in large parenteral or oral doses, a 
number of the aliphatic aldehydes produce anesthesia-like symptoms. 
However, in industrial exposures, this action is minimized because the 
primary irritant action prevents substantial voluntary inhalation. In 
addition, the small quantities that can be tolerated by inhalation are 
usually metabolized so rapidly that no anesthetic symptoms occur. 
Some nausea, vomiting, headache, and weakness have been reported in 
chemists exposed to high concentrations of isovaleraldehyde, but these 
symptoms have not been interpreted as definite anesthetic 
reactions. 3 x 



ORGAN PATHOLOGY 

The principal pathologic conditions produced in animals exposed to 
aldehyde vapors are damage to the respiratory tract and pulmonary 
edema, in general, multiple hemorrhages and alveolar exudate may be 
present, but are usually much less apparent than with gases like 
phosgene. The effects produced by ketene, acrolein, crotonaldehyde, 
and chloracetaldehyde are much more pronounced and similar to those of 
phosgene, and chlorine. High dosages of methylal and furfural have 
been reported to cause various changes in the liver, kidneys, and 
central nervous system, but there has been no confirmation of this 
type of action in human industrial exposures. The aldehydes are 
remarkably free of effects that lead to definite cumulative damage to 
tissues other than effects that may be associated with primary 
irritation or sensitization. 91 



227 
METABOLISM AND MECHANISM OF IRRITATION 

The simple aliphatic aldehydes are oxidized to their corresponding 
fatty acids, which normally undergo fl-oxidation. Urinary metabolites 
are not generally detectable, because the fatty acids are further 
oxidized to carbon dioxide and water. Acetaldehyde is present in 
normal metabolism, and its importance as a metabolite of ethanol is 
well known. In general, the toxicity of aldehydes appears to decrease 
with increasing molecular weight. This relationship is shown by both 
the oral LD^Q and the primary irritant action of the lower- 
molecular-weight substances, which makes them appear to be more 
potent. 31 As shown in Table 8-5, some of the higher aldehydes are 
less toxic than their corresponding alcohols, but the unsaturated 
aldehydes are more toxic than corresponding saturated ones. Although 
primary irritation and contact dermatitis are occasionally seen after 
occupational exposure to aldehydes, there is no evidence of serious 
cumulative effects. 

Evidence from a human chamber-exposure study indicated that 
unsaturation greatly increases the primary irritant activity of an 
aldehyde (Table 8-6). Halogen substitution in aldehydes may also 
greatly increase the local tissue irritation. 31 Dixon 22 has 
postulated that the presence of an aldehyde group adjacent to a double 
bond has a polarizing effect on the latter, which makes the double 
bond capable of adding nucleophilic groups, such as sulfhydryl 
groups. If the sulfhydryl groups in enzymes found in nerve endings 
are attacked, it seems reasonable that this might be related to the 
physiologic response of lacrimation. There are, however, difficulties 
with this explanation, as pointed out by Dixon. 22 The lacrimatory 
action of such materials is usually very transient and ceases 
immediately on removal of the irritant. Dixon speculated that the 
nerve endings may respond to a change in the relative amount of the 
sulfhydryl compound present, but further evidence seems necessary on 
this point, it is interesting that, if exposure to a lacrimator is 
sufficiently prolonged, a point is reached at which lacrimation no 
longer occurs; this suggests complete saturation of some reactive 
site. 31 

The primary irritation is probably associated with the reactivity 
of aldehydes with proteins and amino acids. For example, methylol or 
hydroxymethyl derivatives may be formed from reaction of aliphatic 
aldehydes with amino groups. 

Cyclic compounds may be formed through later reactions. In the 
case of the aromatic aldehydes, the products of reaction with amino 
groups appear to be Schif f bases (C 6 H 5 CH=N-R) . Various types of 
cross-linking reactions can also occur with either aldehydes or 
dialdehydes, resulting in alteration in protein structures. 31 

The aromatic aldehydes are oxidized to their corresponding organic 
acids. The oxidation occurs relatively slowly in the liver, but it is 
usually complete, except where such substituents as hydroxy groups 
make the aldehydes capable of being excreted by alternative metabolic 
pathways, such as sulfate or glucuronic acid conjugations. 31 



228 



TABLE 8-5 
Oral Toxicities of Corresponding Alcohols, Aldehydes, and Acids' 



Oral LD qn in Rats, g/kg 





RCH 9 


Alcohol," 
RCH 9 OH 


Aldehyde , 
RCHO 


Acid, 
RCOOH 


3 


Ethyl 


9-10 


1.93 


3.53 


H 5 


Propyl 


1.87 


1.41 





2 :CH 


Acrylyl 


0.064 


0.046 


2.52 


C 3 H 7 


Butyl 


4.36 


5.89 


8.79 


3 CH:CH 


Crotonyl 





0.3 


1.0 


C 5 H 11 


iso-Butyl 


2.46 
4.59 


3.73 
4.89 


6.44 


Hexyl 


2 H 5 ) 2 CH 


2-Ethylbutyl 


1.85 


3.98 


2.20 


CAH 9 (C 2 H 5 )CH 


2-Ethylhexyl 


3.20 


3.73 


3.00 



leprinted with permission from Williams. 



229 



TABLE 8-6 



Results of Human Exposure to Aldehydes in a Chamber' 



Aldehyde 
Acrolein 



Crotonaldehyde 

Ace t aldehyde 
Propionaldehyde 
Butyr aldehyde 
Isobutyr aldehyde 



Chamber 

Concentration, 

ppm 

0.80 



1.22 



4.1 



134 
134 
230 
207 



Duration of 

Exposure, 

min 

10 



15 

30 
30 
10 
30 



Symptoms 

Extremely irritatir 
lacrimatory (20 s 

Extremely irritatii 
lacrimatory (5s 

Highly irritating <= 
lacrimatory (30 i 

Slightly irritating 
Nonirritating 
Nonirritating 
Nonirritating 



a Data from Sim and Pattle. 96 
Average time after exposure at which lacrimation occurred. 



230 

Aldehydes occur naturally in foods and have been used extensively 
as flavoring agents. The rapid metabolism of the aliphatic and 
aromatic aldehydes by normal pathways undoubtedly accounts for the 
apparent safety of the large number of these substances that are 
ingested by humans and animals. 

Several aldehydes such as those listed in Table Q,-7 have been 
shown to have antineoplastic activity. 87 

It has been demonstrated that several environmental irritants are 
ciliotoxic and mucus-coagulating agents. Aldehydes may thus 
facilitate the uptake of other airborne substances by the bronchial 
epithelium. 



ACETALDEHYDE 

Acetaldehyde is much less irritating to the human eye, nose, and 
throat than formaldehyde or acrolein. Animal studies have shown 
acetaldehyde to have low acute toxicity and no appreciable cumulative 
effects. It does not appear to have substantial mutagenic effects, 
but has been shown, in a single study, to have dose-dependent 
embryotoxic and teratogenic properties. Its carcinogenic potential 
has not been adequately studied. A major source of acetaldehyde in 
man is the metabolism of ethanol. 



ACETALDEHYDE IN ANIMALS 
Acute Toxicity 

By the acute oral route of administration, acetaldehyde is 
slightly toxic, with reported LD5Q values in rats of 1,930 
rag/kg 71 * and 5,300 mg/kg. 70 Its effect on the skin and eyes of 
laboratory animals has not been investigated. Human occupational 
exposure has shown that contact of the eye or skin with liquid 
acetaldehyde can produce painful, but not serious, burns. 61 6I * The 
rapid evaporation of the liquid limits the duration of the 
contact. 61 * Acetaldehyde appears to act as an anesthetic in acute 
inhalation exposures at high concentrations. When exposed at 20,000 
ppm, rats became anesthetized after a brief period of pronounced 
excitement. Half the animals died after 30 mm of exposure; pulmonary 
edema was the principal pathologic finding. The survivors recovered 
in about an hour. 97 In other laboratory animals (mice, rabbits, and 
guinea pigs) , acetaldehyde is slightly to moderately toxic, with 
calculated 4-h LC5Q values of approximately 1,100 ppm. 83 
Subcutaneous-injection studies in rats and mice produced lethal 
effects at 500-600 mg/kg. 9 



Aldehyde 
Glyoxal 

Methylglyoxal 
Kethoxal 



231 

TABLE 8-7 
An tineo plastic Activity of Aldehydes 3 

Active Against 

Leukemia L 1210 

Sarcoma-180 

Sarcoma-180 

Leukemia L 1210 

Sarcoma-180 

Walker-256 

Leukemia L 1210 
Sarcoma-180 
Walker-25b 
Jensen sarcoma 
Lymphosarcoma 



1,4- and 1,5-dicarbonylaldehyde 

Polyaldehydes 

Pyridin-2-carboxaldehyde 

Isoquinolin-1-carboxaldehyde 

Benzaldehyde N-mustards 

Salicylaldehyde and other aromatic aldehydes 



Sarcoma-180 
Sarcoma-180 

Leukemia L 1210 
Sarcoma-180 
Levis-King carcinoma 

Leukemia L 1210 
Sarcoma-180 
Levis-King carcinoma 

Leukemia L 1210 
Walker-25b 
Dunnung leukemia 

Leukemia L 1210 



a Data from Schauenstein et al. 



87 



232 
Extended Studies 

In chronic and subchronic oral studies, acetaldehyde has not 
produced major toxic effects. In a 6-wk subchronic study/ no adverse 
effects on behavior, weight, or condition of the blood were observed 
in groups of 10 rats given 550 or 1,100 mg/kg per day. Pathologic 
examination revealed a statistically significant increase in glycogen 
content of the liver in the 550-mg/kg group, but not in the 
1,100-mg/kg group. Histopathologic examination of the liver revealed 
nonspecific inflammatory and dys trophic changes. A 6-mo oral study 
revealed no adverse effects on behavior or weight in groups of 10 rats 
given up to 50 mg/kg per day. Minimal changes in ECG pattern and 
blood morphology were reported. These effects were reversible; all 
animals returned to normal within a month. 70 

In one inhalation study, groups of 20 hamsters were exposed to 
acetaldehyde at 390, 1,340, or 4,560 ppm, 6 h/d, 5 d/wk for 18 wk. 
The highest concentration induced growth retardation, ocular and nasal 
irritation, increased numbers of erythrocytes in the blood, increased 
heart and kidney weights, and severe histopathologic changes in the 
respiratory tract. The latter consisted of inflammatory changes, 
hyperplasia, metaplasia, and necrosis of the respiratory epithelium. 
The upper respiratory tract was more severely injured than the lower. 
Changes at 1,340 ppra included increased kidney weights in males and 
slight hyperplastic and metaplastic changes of the tracheal 
epithelium. No adverse effects were reported at 390 ppm. 5 " 

Syrian golden hamsters exposed to acetaldehyde vapor at 1,500 ppm 
for 7 h/d, 5 d/wk, for 52 wk developed epithelial hyperplasia and 
metaplasia accompanied by nasal and tracheal inflammation. There was 
no evidence of carcinogenicity produced by acetaldehyde. Some animals 
were exposed to benzo[a]pyrene and diethylnitrosamine to study whether 
acetaldehyde was a cof actor in respiratory tract carcinogenesis. This 
part of the study produced insufficient evidence to determine any 
cof actor effects . 3 la 



Respiratory-System Effects 

The adverse effect of cigarette smoke on the lungs has been 
attributed in part to its acetaldehyde content (0.98-1.31 
mg/cigarette) . 3a This was studied in mice by exposing them to 
acetaldehyde at 1,390 ppm for 30 min twice a day, for 5 wk. A 
reduction in functional residual capacity of the lung similar to that 
seen in animals exposed to cigarette smoke was observed. 116 Other 
studies involving ciliotoxic and cytotoxic effects of tobacco smoke 
and its constituents have indicated that acetaldehyde is an important 
compound in this regard. 38 ?t| 



233 
Cardiovascular-System Effect 

Acetaldehyde, in common with other aliphatic aldehydes, has a 
vasopressor effect i.e., it increases blood pressure. In inhalation 
experiments, marked increases were seen in blood pressure at 
concentrations of 1,665 ppm and higher. 23 When acetaldehyde was 
administered by intraperitoneal injection, vasopressor effects were 
produced at 5-20 mg/kg. At higher doses, a decrease in blood pressure 
was a secondary response to a decrease in heart rate." 



2 6 



Metabolism 

Acetaldehyde is a toxic intermediate in the metabolism of 
ethanol. The main pathway involves an enzyme, alcohol dehydrogenase 
(ADH) . Approximately 90% of the acetaldehyde formed from ethanol is 
oxidized by the liver to acetic acid, which is converted to carbon 
dioxide and water. The ADH-catalyzed oxidation of ethanol to 
acetaldehyde has been extensively reviewed. 30 sa 59 63 108 lla 



Carcinogenic Potential 

The carcinogenic potential of acetaldehyde has not been defined by 
appropriate long-term animal studies. Spindle-cell sarcomas were 
produced in rats given repeated subcutaneous injections but metastasis 
to other tissues was not reported. lls No marked pathologic changes 
were reported in a group of rats fed a diet of ace taldehyde-con tain ing 
rice for more than 300 d. Additional details are not available. 68 



Mutagenic Potential 

Acetaldehyde was not mutagenic in the standard Ames test with 
Salmonella typhimurium. 19 It has some mutagenic activity in the 
fruit fly Drosophila melanogaster , but this activity is much weaker 
than that produced by formaldehyde. 78 The chromosome-breaking 
potential of acetaldehyde has been indicated by the dose-dependent 
sister chromatid exchanges in Chinese hamster ovary cells 69 and 
human lymphocyte chromosomes . B 1 



Embryotoxic and Teratogenic Potential 

Acetaldehyde has shown embryotoxic and teratogenic effects in mice 
similar to those produced by ethanol. Pregnant mice were given 
intravenous injections of acetaldehyde at 40 or 80 mg/kg on days 7, 8, 
and 9 of gestation. Acetaldehyde increased the percentage of embryos 
resorbed and decreased their weight and their protein content. 
Teratogenic effects included anomalies in closure of the cranial and 
caudal regions of the neural tube. 73 



234 

HUMAN INVESTIGATIONS 

Because of the explosive hazards of acetaldehyde, it is usually 
handled in closed systems in industry and exposures are not apt to be 
continuous or large. Therefore, occupational-exposure data are 
lacking. 

Acetaldehyde is readily detected well below 50 ppm. Some persons 
can notice it below 25 ppm. At 50 ppm, a majority of volunteers 
exposed for 15 min had some eye irritation; and at 200 ppm, all 
subjects had redness of the eyes and transient conjunctivitis. 31 

Eye irritation and, to a lesser extent, nose and throat irritation 
are the only signs noted during exposure to the usual concentrations 
encountered industrially. 31 The odor and eye-irritation thresholds 
are 0.07 ppm* and 50 ppm, 6 respectively. The TC Lo (lowest toxic 
concentration) for an observed health effect after inhalation is 134 
ppm, and the threshold limit value is 200 ppm. 6 Acetaldehyde can 
cause narcosis, bronchitis, albuminuria, fatty degeneration of the 
liver, and pulmonary edema at high concentrations. Lethal doses cause 
progressive slowing of heart and respiratory rates followed by 
respiratory paralysis. There have been very few studies of persons 
after industrial exposure. In one case, chronic exposure of workers 
to acetaldehyde at 0.5-22 mg/m 3 (0.21-9.36 ppm) caused irritation of 
the mucous membranes. 21 

There have been many reports of the pharmacology of acetaldehyde 
in relation to the effects of alcohol. Human subjects were given 
intravenous infusions to increase blood concentrations to 0.2-0.7 mg% 
(about 10 times normal). At these concentrations, heart rate and 
respiratory ventilation were increased, and a "hangover" sensation is 
noted. 31 

Bittersohl 1 1 reported an increased prevalence of malignant 
tumors in aldehyde workers. Of the 220 people employed in a plant, 
150 had been employed for more than 20 yr. Nine neoplasms were noted 
in males: two squamous-cell carcinomas of the oral cavity, one 
adenocarcinoma of the stomach, one adenocarcinoma of the cecum, and 
five squamous-cell carcinomas of the bronchial tree. The workers had 
mixed exposures that included acetaldehyde, butyraldehyde, 
crotonaldehyde , higher condensed aldehydes, butanol, hexatriol, 
hexatetrol, octadiol, and butadiene. Of the nine employees, eight 
smoked 5-10 cigarettes per day. 



ACROLEIN 

Acrolein is highly toxic by all routes of administration. Its 
vapors cause severe respiratory and ocular irritation. Contact with 
liquid acrolein can produce skin or eye necrosis. Serious injury is 
produced even by a 1% aqueous solution. Acrolein has not been shown 
to be carcinogenic or embryotoxic, but appears to be mutagenic in some 
nonmammalian systems. 



235 

ACROLEIN IN ANIMALS 
Acute Toxicology 

By the oral route of administration, acrolein is highly toxic, 
with reported LDgg values in rats, mice, and rabbits of 46 
mg/kg, 100 40 mg/kg, 13 and 7.1 mg/kg (Shell Chemical Company, 
unpublished data) , respectively. Acrolein is easily absorbed through 
the skin of rabbits in lethal amounts (LD5Q, 168-562 mg/kg) (Shell 
Chemical Company, unpublished data; Union Carbide Company, unpublished 
data) . When applied undiluted, acrolein causes necrosis; even a 1% 
aqueous solution can produce a burn on the abdominal skin of rabbits. 

Likewise, instillation of a 1% solution into the rabbit eye caused 
severe injury. 100 

The marked toxicity of acrolein has also been shown by inhalation 
exposures. In a 30-min exposure of rats, the LC^Q was 131 ppm; 97 
in a 4-h exposure, it was 8 ppm. 100 

Correspondingly low values have been reported for other species of 
animals. Acrolein vapors are also very irritating to the eyes, nose, 
and throat of laboratory animals, as well as man. Exposure of cats 
and rats at approximately 12 ppm caused severe symptoms of eye and 
respiratory tract irritation." * 66 

Injection studies have demonstrated the high acute toxicity of 
acrolein, with lethal doses of 30-50 mg/kg. 97 



Extended Studies 

Acrolein was added to the drinking water of rats, and that water 
was administered as their only source of water for up to 90 d. The 
unpalatability of the water was manifest in reduced body weights and 
increased kidney weights. The death of animals given water containing 
acrolein at 600-1,800 ppm was due to lack of water intake. No adverse 
pathologic or hematologic changes were observed (G.W. Newell, 
unpublished data; Union Carbide Company, unpublished data) . 

Continuous inhalation of acrolein by rats for up to 90 d had 
little or no effect at concentrations of 0.06-0.22 ppm. 12 ** 60 
Dogs and monkeys appeared to be more sensitive to the vapors of 
acrolein. in one of these studies, 60 no abnormal behavior was seen 
at 0.22 ppm, but pathologic examination revealed acrolein-related 
changes in the tracheas of the monkeys and lungs of the dogs. Higher 
concentrations (1-1.8 ppm) produced visible signs of ocular and nasal 
irritation throughout the 90-d period. In another study, 12 exposure 
of rats at 0.55 ppm produced signs of irritation that subsided after 
3-4 wk. The mean body weight of exposed animals was also 
significantly lower than that of the controls. At 1-2 ppm, acrolein 
induced minimal biochemical, pathologic, and functional injury of the 
lower respiratory tract. The changes which included a decrease in 
urinary vanillyl-mandelic acid and inflammatory infiltrates with mild 
perivascular edema in the respiratory tract reached a peak during the 
first month of exposure and then subsided. 39 



236 

During a continuous-inhalation study, groups of hamsters, rats, 
and rabbits were exposed to acrolein at 0.4, 1.4, and 4.9 ppm for 6 
h/d, 5 d/wk for 13 wk. Marked changes in the nasal epithelium were 
evident in all species at the highest concentration. Histopathologic 
examination revealed necrotizing rhinitis and squamous hyperplasia and 
metaplasia of the epithelium. Rats appeared to be the most 
susceptible species examined, with acrole in-related abnormalities 
associated with 0.4 ppm exposure. This concentration was nontoxic to 
both hamsters and rabbits. 3lf Lyon et^al^ 60 exposed rats, guinea 
pigs, monkeys, and dogs to acrolein at 0.7 and 3.7 ppm for 8 h/d, 5 
d/wk, for 6 wk or 24 h/d for 90 d at 0.21-1.8 ppm. No clinical signs 
of toxicity were observed up to 0.7 ppm. Dogs and monkeys were 
visibly affected by respiratory irritation at the greater exposures. 
Repeated exposures at 0.7 ppm produced chronic inflammatory changes, 
and 3.7 ppm caused squamous metaplasia of the lungs in monkeys. 
Continuous exposure at 0.22 ppm resulted in moderate emphysema, acute 
congestion of the lungs, and squamous metaplasia and oasal cell 
hyperplasia of the trachea. 

In a chronic study, 36 hamsters were exposed at 4.0 ppm, 7 h/d, 5 
d/wk for 52 wk. The irritation produced by this concentration of 
acrolein was initially manifest by salivation, nasal discharge, 
restlessness, and the animals' keeping their eyes closed. The animals 
apparently became acclimated to the vapors and behaved normally after 
the second week of exposure, except for increased restlessness 
(compared with the controls) . At the end of the exposure period, six 
animals were sacrificed and the rest held for an additional 29-wk 
recovery period. The animals exhibited rhinitis and hyperplastic and 
metaplastic changes of the nasal epithelium. 33 No evidence of 
carcinogenicity was seen. 



Respiratory-System Effects 

Groups of mice and guinea pigs were exposed to low concentrations 
of acrolein. In mice, a concentration of 1.7 ppm produced a 50% 
decrease in respiratory rate. 50 Another group was exposed to a 
mixture of acrolein and formaldehyde. A 50% decrease in respiratory 
rate was produced at a combination of 1.87-ppm acrolein and 1.42-ppm 
formaldehyde; hence, the effect is not additive. 1 * 9 A group of 
guinea pigs exposed to acrolein at 0.4-1.0 ppm for 2 h showed definite 
decreases in respiratory rate. 67 in a study with dogs, it was shown 
that acrolein is taken up more readily by the upper respiratory 
system, but the uptake is considerably less than that of 
formaldehyde . 2 * 



Cardiovascular -System, Effects 

Acrolein, in common with many other aldehydes, causes an increase 
in blood pressure (vasopressor effect) . Anesthetized rats were given 
acrolein at 0.05-5.0 mg/kg by intravenous injection or exposed at 



237 

4.4-2,200 ppm for 1 min. With intravenous doses up to 0.25 mg/kg, an 
increase in blood pressure predominanted as an effect. At higher 
doses, a decrease in blood pressure predominated. With exposure by 
inhalation, a vasopressor effect of increasing magnitude was observed 
within 15 s after the onset of exposure. Within 10 s after exposure 
ceased, there was a rapid return to normal. 25 



Metabolism/Pharmacokinetics 

Acrolein is formed during thfe degradation of oxidized spermine and 
spermidine. It is a probable metabolite of allyl alcohol and has been 
shown to be a metabolite of the antitumor agent cyclophosphamide. 21 



Carcinogenic Potential 

Acrolein was not carcinogenic in a 52-wk inhalation study in 
hamsters. 33 Preliminary results from an NCI-sponsored inhalation 
study, also in hamsters, confirm this conclusion. 21 Acrolein did 
not produce sarcomas in a subcutaneous-injection study in mice. 105 
When tested by skin application in a promotion-initiation study with 
croton oil, acrolein had little or no tumor-initiating activity. 82 
Similarly, it had no effect on the carcinogenic activity of 
diethylnitrosamine and had a minimal effect on the activity of 
benzo[a]pyrene. 39 



Mutaqenic Potential 

Acrolein showed some mutagenic activity in the Ames test. 
Mutagenic effects were observed in Salmonella typhimurium strains TA 
1538 and TA 98 (strains that detect frameshift mutations) , whereas no 
activity was seen in strains TA 1535 and TA 100 (strains that detect 
base-pair substitutions) . 9 In another test of the Ames type, 
acrolein did not induce point mutations in eight strains of 
histidine-dependent mutants of S_. typhimurium. The authors indicated 
that this test might not be able to identify weak mutagens. 7 
Acrolein had mutagenic activity in the fruit fly Drosophila 
melanogaster 7 8 and in a DNA-polymerase-def icient Escherichia 
coli. 10 However, no activity was seen in strains of J. coli capable 
of detecting forward and reverse mutations. 27 28 No activity was 
seen in yeast Saccharomyces cerevisiae* 5 or in a dominant-lethal 
assay in mice. 29 



Embryotoxic and Teratogenic potentiaJL 

Acrolein did not exhibit embryotoxicity in an inhalation study in 
rats. Male and female rats were continuously exposed at 0.55 ppm and 
allowed to mate after the fourth day of exposure. No significant 



238 

differences could be observed at this low concentration between 
control and test animals in number of pregnant animals, number of 
fetuses, or mean fetal weight. 12 The fetuses were not examined for 
malformations; therefore, no information on teratogenic potential is 
available from this study. No evidence of teratogenicity was observed 
in embryos from acrolein-treated chicken eggs. 51 



ACROLEIN IN HUMANS 

Acrolein is predominantly an ocular and respiratory irritant. Its 
toxicity can involve the senses, reflexes, nervous system, and 
respiratory system, alter biochemical reactions, and affect the 
composition of blood at 0.2-6.0 ppm. 17 Its conjugated unsaturated 
bonds at the 1,2-position result in eye irritation (threshold, 0.2 
ppm 17 ) 2.5 times greater than that from formaldehyde. 2 At higher 
concentrations (0.5-1.0 ppm), this difference increases to 4-5 
times. l Such irritancy is particularly important, because acrolein, 
as a partially oxidized organic emission, is a major contributor to 
the irritant quality of cigarette smoke 117 and photochemical 
smog. 17 Acrolein in Los Angeles smog was thought to be responsible 
for 35-75% as much eye irritation as formaldehyde (the major aldehyde 
in auto exhaust). 2 The occupational threshold limit value for 
acrolein (0.1 ppm) is low enough to minimize irritation in exposed 
persons: 0.25 ppm is considered to be moderately irritating, 0.5 ppm 
is thought to be a practical working concentration, and 1 ppm causes 
marked irritation of the eyes and nose with lacrimation in less than 5 
min. 

The principal site of attack of acrolein is the mucous,, membranes 
of the upper respiratory tract; high concentrations can produce 
pulmonary edema. Table 8-8 lists human responses to various 
concentrations of acrolein. The results of several studies concerning 
eye irritation are found in Table 8-9. 

Descriptions of acrolein toxicity are largely in the form of 
ocular-irritation studies. However, the conclusions drawn from these 
studies should be tempered, because the relationships between 
atmospheric acrolein concentrations and indexes of eye irritation are 
nonlinear and subject to a large element of variability. 72 79 
Ocular exposure to 0.5% acrolein for 5 rain 95 caused discomfort with 
stinging in 30-60 s and lacrimation, pain, and eyelid flickering and 
heaviness in 3-4 min. Attesting to the variability of ocular 
response, a chronaximetric study of the eyes of three persons showed 
reduced chronaxy in two subjects at 0.64 ppm, but prolonged chronaxy 
in the third. The optical-chronaxy reflex threshold was determined to 
be about 0.7 ppm. Similarly, sensitivity to light was increased or 
decreased and then gradually returned to normal. The optical-chronaxy 
method of eye-irritation detection may not be sensitive enough, 
inasmuch as other studies 17 H 3 e7 117 have indicated lower 
eye-irritation thresholds measured by the more subjective methods of 
blink response, lacriroation, or pain response. 



239 



TABLE 8-8 
Thresholds of Response after Exposure to Acrolein 



Acrolein 
Concentration, ppm 

0.2 a 

0.33-0.40 a 

0.40-l.U 

0.62 

0.73 

0.8 

1.0 

5.5 

_>10.0 (vapor, estimated) 

24.0 



Response 

Eye-irritation threshold 1 
Odor threshold 3 ' 6 ' 87 
Prolonged deep respiration 



87 



Respiratory-response threshold 



6 



Chronaxime trie-response threshold 
Severe mucosal irritation 
Immediately detectable 
Intense irritation 
Lethal in a short time 
Unbearable 



6,77 



a ln a simulated-smog study, the acrolein eye-irritation threshold (withou 
olfaction) for a 30-s exposure was 1.27 ppm, and the odor threshold was 
0.08-0.29 ppm. 1 The eye-irritation threshold was the same whether dete 
mined by increasing concentrations over a constant period or by increasi 
the duration of exposure over a series of concentrations (M. Jones, 
H. Buchberg, K. Lindh, and K. Wilson, unpublished data). 



240 



TABLE 8-9 
Ocular Response to Airborne Acrolein a 



Ocular Exposure Duration of 
Concentration, ppm Exposure Effect 

0.8 10 min Extremely irritating; only just tolerable 

1-2 5 min 87% of test panel reported irritation 

1 5 rain 82% of test panel reported irritation 

0.5 5 min 35% of test panel reported irritation 

0.5 5 min 19% of test panel reported irritation 

0.5 12 min 91% of test panel reported irritation 

1.8 30 s (Odor) 

1 min Slight irritation 

2 min Distinct irritation (and slight nasal 

irritation) 
4 min Profuse lacrimation; practically 

intolerable 
5.5 5s Moderate irritation (and odor and 

moderate nasal irritation) 
20 s Painful irritation (and painful nasal 

irritation) 

60 s Marked lacrimation; practically intoleral 
21.8 Intolerable 

30.25 5 min Moderate irritation 

4 5 min Severe irritation 

0.06 Irritation 0.471 on scale of 0-2 

1.3-1.6 Irritation 1.182 on scale of 0-2 

2.0-2.3 Irritation 1.476 on scale of 0-2 



a. 48 

Reprinted with permission from Kane. 



241 

Inhalation of acrolein at 0.22-0.75 ppm 87 has generally resulted 
in a depressed respiratory rate due to its anesthetic effect, 77 I17 
although 1 ppm has been found to be tolerated with no significant 
respiratory change. ^ Higher inhaled concentrations result in 
respiratory irritation. The TC Lo for irritation of the upper 
respiratory tract is 1 ppm, 11 although nasal irritation occurs at 
lower concentrations. 21 " 3 e7 

In liquid form, acrolein causes severe skin irritation. 5 Dermal 
application of a 1% solution produced a positive patch test. 21 

The effects of acrolein on biochemical functions have not been 
thoroughly studied. 21 87 At 0.22 ppm or higher, prolonged 
inhalation caused a reduction in lung lactic dehydrogenase. Acrolein 
is highly reactive with thiol groups (this is related to its 
lacrimatory effect) , and it can rapidly conjugate with glutathione and 
cysteine. Acrolein is also a potent in vitro inhibitor of human 
polymorphonuclear leukocyte chemotaxis (EC 5 Q, 15 urn) , but has no 
effect on leukocyte integrity or glucose metabolism. Chemotaxis is 
assumed to be inhibited by the reaction of acrolein with essential 
thiol groups of cellular proteins involved in chemotaxis. A decrease 
in cholinesterase activity and an alteration of liver enzyme activity 
have also been noted. 87 

Industrially, acrolein is expected to cause serious intoxication 
only rarely, because of human intolerance of its irritating effects. 
The inhalation LC^Q (lowest lethal concentration) for humans has 
been estimated at 153 ppm for a 10-min exposure. 101 * Two cases of 
occupational poisoning (one fatal) have been reported. 81 * It is 
speculated that the greatest occupational danger of acrolein poisoning 
is associated with the welding of fat and oil cauldrons. 

The EPA has determined that, for protection of human health from 
the toxic properties of acrolein ingested through water and 
contaminated aquatic organisms and through contaminated aquatic 
organisms alone, the ambient-water criteria are 0.320 and 0.780 mg/L, 
respectively. 1I2 



OTHER ALDEHYDES 

Tables 8-2, 8-3, and 8-4 list toxicity information on other common 
aldehydes. The eye and respiratory tract irritation caused by 
formaldehyde, acrolein, and, to some extent, acetaldehyde is also 
caused by propionaldehyde , 9 6 10 butyraldehyde (Sim and Pattle; 96 
Smyth et^al^; 100 * * Du Pont Company, unpublished data), and chloral 
(Du Pont Company, unpublished data) . Chloral is unique, in that its 
inhalation toxicity puts it in the highly toxic category (Du Pont 
Company, unpublished data). However, it is widely used as a sedative. 
Chloral has also been shown to be mutagenic in the Ames test (Minnich 
e_t_al_. ; 65 Du Pont Company, unpublished data) and has shown some 
embryotoxic properties. 110 None of the other aldehydes have 
toxicity values that would be inconsistent with the values typical of 
their class. 



242 
BENZALDEHYDE 



No information is available on the human health effects of 
benzaldehyde . Increased concentrations were found in the blood of New 
Orleans residents during 1970-1975. 57 



BUTYRALDEHYDE AND ISOBUTYRALDEHYDE 

These aldehydes are not human irritants. The estimated inhalation 
TC Lo of butyr aldehyde 101 * is 580 mg/m 3 . Exposure at 200 ppm for 
30 min results in no irritant effects. 5 However, isobutyr aldehyde 
at the same concentration causes nausea. 6 Butyraldehyde has been 
implicated 11 as an etiologic factor in the cancer epidemiologic 
study discussed in the section on acetaldehyde. 



CHLORAL HYDRATE 

Chloral hydrate is converted to trichloroethanol and 
trichloroacetic acid in man. Some of the alcohol derivative is 
excreted as the glucuronide. Bromal hydrate is metabolized 
differently and is more toxic. 31 



CHLOROACETALDEHYDE 

Chloroacetaldehyde is somewhat more irritating to the eye, nose, 
and throat than is formaldehyde. Contact with a 40% aqueous solution 
produces serious eye injury and skin corrosion. 1 * Dilute aqueous 
solutions of 0.1% are capable of causing marked skin irritation. The 
carcinogenic activity of vinyl chloride has been attributed to its 
metabolic activation in the liver to 2-chloroacetaldehyde. 
2-Chloroacetaldehyde increases the revertant power of 3. typhimurium 
mutant strains; this suggests that the presence of an oxidase in the 
microsomal fraction of human liver is responsible for converting vinyl 
chloride to mutagenic metabolites. 8 



CROTONALDEHYDE (R -METHYL ACROLEIN) 

Crotonaldehyde , whose threshold limit value of 2 ppm is based on 
animal studies, 1 * produces symptoms similar to those produced by 
acrolein. A strong odor is detectable at 15 ppm, and exposure at 45 
ppm results in disagreeable, conjunctival irritation. An increased 
cancer incidence in workers exposed to crotonaldehyde and other agents 
is discussed in the section on acetaldehyde. 11 



243 

FURFURAL 

There are conflicting reports on the toxicity of furfural. One 
report indicating only mild effects contrasts with another describing 
numbness of the buccal membranes and tongue, loss of taste, and 
respiratory distress. 81 * The latter report indicated that 1.9-14 ppm 
caused bloodshot eyes, lacrimation, throat irritation, headache, and 
possibly damage to eyesight. Furfural is metabolized by conversion of 
the aldehyde group to an acid and conjugation with glycine. 31 Other 
than an occasional allergic skin manifestation, no injury from 
occupational exposure to furfural has been reported. 31 The 
inhalation TCLo has been estimated 101 * at 600 yg/m 3 . As a 
result of the primary irritation induced by furfural, a threshold 
limit value of 5 ppm has been established. 

Feron 32 conducted an intratracheal-instillation study in Syrian 
golden hamsters with furfural, benzo[a]pyrene, and benzo[a]pyrene plus 
furfural. Furfural alone produced no evidence of carcinogenic 
activity, but the results suggested a cocarcinogenic effect of 
furfural on the respiratory tract of hamsters. In comparison with 
treatment with benzo[a]pyrene alone, intratracheal instillation of 
benzo[a]pyrene plus furfural resulted in earlier development of 
metaplastic changes of the tracheobronchial epithelium, a shorter 
latent period for tracheobronchial tumors, and a few more bronchial 
and peripheral squamous-cell carcinomas. 



GLUTARALDEHYDE 

Glutaraldehyde is a strong nasal irritant and a mild optic or 
dermal irritant. Occasional dermal contact can cause an allergic 
response leading to contact dermatitis. Activated glutaraldehyde (pH, 
7.5-8.0) is a stronger irritant and affects the upper respiratory 
tract. Occupationally, a 2% aqueous solution (0.38 ppm) in an 
operator's breathing zone produces severe eye, nose, and throat 
irritation and headache. This has led to the establishment of a 
threshold limit value (ceiling) of 0.2 ppm. " 

Glutaraldehyde at 5-10% has been effective in reducing 
hyperhidrosis. 20 36 37 l * 7 86 Sensitization to glutaraldehyde occurs 
much less frequently than sensitization to formaldehyde, and 
cross-reaction of formaldehyde-sensitive subjects does not seem to 
occur. i Strong staining of the skin limits the usefulness of 
glutaraldehyde. As with formaldehyde, the blockage of sweating can be 
reversed by stripping the stratum corneum with tape. 36 75 e6 



GLYOXAL 

The antitumor activity of glyoxal has been mentioned. 87 
Concentrations of 0.5 mM or higher inhibit human fibroblast cell 
division and synthesis of DNA, RNA, and proteins. 8 



244 
4 -HYDROXYPENTENAL 

This compound inhibits mitosis in human kidney cells and is 4 
times as active an inhibitor as kethoxal. 87 

KETOALDEHYDES 

Ketoaldehydes complexed with hydrogen sulfite and an ammo group 
were less harmful than free aldehydes in tumor therapy. These 
complexes showed significant antitumor activity in in vitro 
adenocarcinomas cultured from breast and colon tissues and in 
epidermal carcinoma. 87 

MALONALDEHYDE 

Reaction of malonaldehyde (50 yg/ml) with DNA from human 
fibroblasts reduces hypochroraia, changes the "temperature-absorption 
curve," and increases resistance to degradation by DNase. 87 
Malonaldehyde is a product of peroxidative fat metabolism and is 
formed in the tissues of animals whose diet is deficient in 
antioxidants. Shamberger ejt ail. 9 3 applied malonaldehyde once to the 
shaved backs of female Swiss mice. Daily treatment with 0.1% croton 
oil produced tumors in 52% of the mice at 30 wk. Malonaldehyde 
concentrations in mouse skin increased after application of 
benzo[a]pyrene, 7, 12-dimethylbenz [a] anthracene, and 
3-methylcholanthrene. A weak link has also been established from 
epidemiologic data between beef fat in the diet, malonaldehyde content 
in beef, and the incidence of large bowel cancer. 91 See the 
discussion in Schauenstein _et jal. 8 7 (Chapter 5) for additional 
discussion of the metabolism of malonaldehyde. 

PROPIONALDEHYDE AND AMINOPROPIONALDEHYDE 

Inhalation of propionaldehyde at 134 ppm for 30 mm, or 0.1-6.0 
ug/m f has been demonstrated to cause mild irritation of mucosal 
surfaces. 6 21 8 -Aminopropionaldehyde is a natural component of 
human serum. A decrease in its oxidation leads to its accumulation, 
with an additional accumulation of spermidine and a decrease in 
malonaldehyde. Increases in propionaldehyde and spermidine cause an 
increase in RNA synthesis. 87 Propionaldehyde is a skin carcinogen 
whose structure resembles that of malondialdehyde. 9 2 

SYNAPALDEHYDE (CINNAMALDEHYDE) 

Cinnamaldehyde is a natural ingredient in the essential oils of 
cinaramon leaves and bark, hyacinth, and myrrh. It is used primarily 
as a fragrance in soaps, creams, lotions, and perfumes. 



245 

Cinnamaldehyde is oxidized to cinnamic acid, which is further degraded 
to benzoic acid; 118 much of it shows up in the urine of rats as 
hippuric acid. x 9 

When administered by intubation to rats and guinea pigs, cinnamic 
aldehyde had an LD 50 of 2,220 and 1,160 mg/kg, respectively. The 
toxicity in rats was expressed as depression, diarrhea, and a scrawny 
appearance. * 6 The intraperitoneal LD 50 of Cinnamaldehyde in mice 
was 2,318 rag/kg, and its oral LD 50 in rats was 3,350 mg/kg. 

In a study of the toxicity of synthetic and natural products, the 
LD 100 s in mice were 6,000 and 12,000 mg/kg, respectively. In 
chronic-toxicity studies, liver lipid content was reportedly increased 
by 20% in the first generation and 22% in the second generation. 103 

Published reports indicate that Cinnamaldehyde is a skin irritant 
and strong sensitizer. Sensitization reactions have been produced in 
guinea pigs after challenge with 0.5% Cinnamaldehyde by the method of 
Buehler. 107 Kligman 52 53 tested Cinnamaldehyde on human subjects 
at 3% and 8% in petrolatum. The lower concentration produced no 
irritation, but the 8% concentration was severely irritating. Studies 
completed by the North American Contact Dermatitis Research Group 
indicated that Cinnamaldehyde may be a frequent cause of allergic 
reactions to perfumes. 89 This Group and Schorr 90 reported 
positive reactions to Cinnamaldehyde in more than 3% of those tested. 

When tested in rabbits, Cinnamaldehyde converted resting EEC 
patterns to arousal patterns in the gallamine-paralyzed preparation 
with the intact brain. A centrally originating deactivation was 
produced through direct and indirect excitatory action on the 
brainstem reticular formation. 1 * 1 It also produced positive 
inotropic and chronotropic effects in isolated guinea pig heart 
preparations and hypotensive effects in anesthetized dogs and guinea 
pigs secondary to its peripheral vasodilatation. l * 2 

Cinnamaldehyde was shown to be weakly mutagenic, with a tendency 
to produce nondis junction in tests using late embryos and young larvae 
of Drosophila melanogaster . : x ** The incidence of primary lung tumors 
in both male and female A-strain mice was not increased over control 
values after intraperitoneal injection at 4.00 or 0.8 g/kg over an 
8-wk period. 106 

Epidemiologic evidence from a study in Buckinghamshire in 
Oxfordshire, England, suggested increased nasal and sinus cancers in 
woodworkers of the furniture industry. l Other investigators have 
not found a relationship between occupation and nasopharyngeal cancer 
in retrospective surveys. 18 56 62 9 * Nasopharyngeal cancers are 
apparently found in a wide variety of occupations, and Buell, 16 
using occupation as an indicator of economic status, found a twofold 
excess of nasopharyngeal cancers among those of lower socioeconomic 
status. 

As a result of these epidemiologic findings, a number of 
constituents of wood are being tested for carcinogenic activity, 
including the lignin constituents, methoxy-substituted 
cinnamaldehydes, and cinnamalcohols. The latter would yield respective 
aldehydes in the course of metabolic oxidation by alcohol 
dehydrogenases. Preliminary data indicate that 3,4,5- 



246 

trimethoxycinnamaldehyde is a potent carcinogen and may be involved in 
the carcinogenic action of some woods and their products. 88 
Cinnaraaldehyde has not been shown to be carcinogenic, but 
glycidaldehyde (2,3-epoxypropionaldehyde) has been shown to be 
carcinogenic in mice and rats. 113 

HeLa cells in permanent culture suffered irreversible damage from 
exposure to 50 mM glycer aldehyde, with high toxicity at concentrations 
lower by a factor of 10-100. 87 The HeLa cells produced 
4-hydroxy-2-oxobutanal as a bacteria-inhibiting factor. 87 



VALERALDEHYDE AND I SOVALERALDEHYDE (2-METHYLBUTYRALDEHYDE) 

Human data on valeraldehyde are not available. A threshold limit 
value of 50 ppm is based on animal data. 1 * Several chemists engaged 
in distilling i sovaler aldehyde 3 l developed chest discomfort, nausea, 
emesis, and headaches. Although exposures were not measured, the odor 
was pronounced, and ambient concentrations may have been high. All 
symptoms were reversed within a few days without further consequence. 



MISCELLANEOUS 

Eye Irritation from Oxidation Products of Paraffinic, Olefinic, and 
Aromatic Hydrocarbons and Aldehydes 

Photochemical auto smog consists largely (ca. 15%) of unburned and 
partially oxidized organic materials, including aliphatic, olefinic, 
and aromatic hydrocarbons, and aldehydes. Gaseous NO-^ is also 
present as an oxidant. 17 

Chemical reactivity increases in the order of paraffinic 
hydrocarbons < ethylene, toluene, propionaldehyde < 1-butene, 
1,3-butene, 1,3,5-trimethylbenzene. 3 In measurements of human eye 
irritation caused by oxidation products of these compounds combined 
with NOx, 1,3-butadiene proved to be the most potent (eye irritation 
index, 20 on a 1-30 scale). Less-saturated or shorter-chain olefins 
produced less eye irritation, and isolated oxidized olefins at 
concentrations of less than 1 ppm produced no irritation. Of the 
aromatic hydrocarbons, 45% oxidation of mesitylene to aliphatic 
aldehydes produced only slight eye irritation (index, 6 on a 1-30 
scale). In contrast with the strong irritating effect of oxidized 
olefinic hydrocarbon mixtures, olefinic and aromatic hydrocarbons 
together, when oxidized, produced only slight irritation. Oxidation 
of 3.5-ppm propionaldehyde produced 0.08-ppm formaldehyde, which 
resulted in moderate eye irritation (index, 8 on a 1-30 scale) . Lower 
propionaldehyde concentrations resulted in only slight irritation. 3 
In combination with acetaldehyde , oxidation resulted in eye irritation 
of 0.2-2.1 on a scale with an upper limit of 5. 2 For constituents 
of photochemical smog, variations in eye-irritation threshold appear 
to be due to the amount of unsaturated hydrocarbon present in the 
smog. The thresholds of saturated hydrocarbons oxidized to saturated 



247 



aldehydes are lower than expected. This suggests the presence of 
unsaturated aldehyde (e.g., acrolein) resulting from the oxidation of 
unsaturated precursors. 15 



^Naturally Occur rinq Aldehydes 

In addition to the presence of propionaldehyde as a natural 
constituent of human blood, several other aldehydes are also natural 
body constituents. Some of these higher, naturally occurring 
aldehydes and their functions are as follows: 87 

Indol-3-ylacetaldehyde J Metabolic products of tryptophan 
5-Hydroxyindol-3-ylacetaldehyde / 

Pyridoxal phosphate and pyridoxal Coenzymes and catalysts 
Retinal and dehydroretinal Vitamins A! and A 2 / 

respectively; parts of the 

light-sensitive optic pigments 

(rhodopsin) 
Collagenaldehyde Part of the collagen 

cross-linkage reaction mechanism 

These and other aldehydes (formaldehyde, acetaldehyde, 
butyr aldehyde, isobutyraldehyde, and crotonaldehyde) are oxidized to 
the acid form by formyl hydrate dehydrogenase , which is in human blood 
serum. 87 



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food additives and chemotherapeutic agents by the pulmonary 
tumor response in strain A mice. Cancer Res. 33:3069-3085, 1973. 

107. Suskind, R. R. , and V. A. Majeti. Occupational and 
environmental allergic problems of the skin. J. Dermatol. 3:3, 

1976. . 

108. Teschke, R. , Y. Hasumura, and C. S. Lieber. Hepatic pathways of 
ethanol and acetaldehyde metabolism and their role in the 
pathogenesis of alcohol-induced liver injury. Nutr. Me tab. 21 

(Suppl. 1) -.144-147, 1977. 

109. Teuchy, H., J. Quatacker, G. Wolf, and C. F. Van Sumere. 
Quantitative investigation of the hippuric acid formation in the 
rat after administration of some possible aromatic and 
hydroaromatic precursors. Arch. Int. Physiol. Biochim. 79:573, 

1971. 

110. Tittmar, H. G. Some effects of ethanol, presented during the 
pre-natal period, on the development of rats. Br. J. Alcohol 
Alcohol. 12:71-83, 1977. _ 

111. U.S. Department of Health, Education, and Welfare, Public Health 
Service, Center for Disease Control, National Institute for 
Occupational Safety and Health. National Occupational Hazard 
Survey, conducted 1972-1974. Computerized data file. 1980. 

112. U.S. Environmental Protection Agency, Office of Water 
Regulations and Standards. Ambient Water Quality Criteria for 
Acrolein. U.S. Environmental Protection Agency Report No. EPA 
440/5-80-016. Washington, D.C.: U.S. Government Printing 
Office, 1980. 100 pp. 



255 

113. Van Duuren, B. L. , L. Langseth, L. Orris, M. Baden, and M. 
Kuschner. Carcinogenicity of epoxides, lactones, and peroxy 
compounds. V. Subcutaneous injection in rats. J. Nat. Cancer 
Inst. 39:1213-1216, 1967. 

114. Venkatasetty, R. Genetic variation induced by radiation and 
chemical agents in Drosophila melanogaster . Dissertation. 
Bowling Green, Kentucky: Bowling Green State University, 1971. 
138 pp. 

115. Watanabe, P., and S. Sugimoto. Study on the carcinogenicity of 
aldehyde. 3rd report. Four cases of sarcomas of rats appearing 
in the areas of repeated subcutaneous injections of 
acetaldehyde. GANN 47:599-601, 1956. (in Japanese) 

116. Watanabe, T. , and D. M. Aviado. Functional and biochemical 
effects on the lung following inhalation of cigarette smoke and 
constituents. II. Skatole, acrolein, and acetaldehyde. 
Toxicol. Appl. Pharmacol. 30:201-209, 1974. 

117. Weber-Tschopp, A., T. Fischer, R. Gierer, and E. Grandjean. 
Experimentally induced irritating effects of acrolein on 
humans. Int. Arch. Occup. Environ. Health 40:117-130, 1977. 

118. Williams. R. T. Detoxication Mechanisms. The Metabolism and 
Detoxication of Drugs, Toxic Substances and Other Organic 
Compounds. 2nd ed. New York: John Wiley & Sons, Inc., 1959. 
796 pp. 



CHAPTER 9 
EFFECTS OF ALDEHYDES ON VEGETATION 



For over 80 yr, formaldehyde was assumed to play an important role 
in plant metabolism as the first product of photosynthesis. According 
to the hypothesis of the German chemist von Baeyer, carbon dioxide 
absorbed from the air was dissociated by green plants into carbon 
monoxide that was reduced to formaldehyde, which in turn polymerized 
to a carbohydrate. 10 However, experimental evidence never supported 
this hypothesis. Researchers were unable to distill formaldehyde from 
huge quantities of leaves or to enhance sugar production in leaves by 
adding formaldehyde. As the concept of the essentiality of 
formaldehyde in plants faded, the phytotoxic nature of the compound 
began to emerge. Once Benson and Calvin had demonstrated that 
3-phosphoglyceric acid was the first product of photosynthesis, 
further interest in formaldehyde was focused on its phytotoxicity . 

The greatest incentive for the investigation of aldehydes as a 
class of compounds was probably the occurrence of photochemical smog 
in California and other highly populated areas of the United States in 
1945. Although hydrocarbons and oxides of nitrogen were suspected of 
being the principal reactants in smog, 8 the specific pollutants 
responsible for plant damage had not been identified. Several groups 
of investigators experimentally subjected intact plants or plant parts 
to known doses of artificially generated aldehydes and then described 
symptom development or measured the impairment of some physiological 
process. 

In addition to these investigations related to ambient air 
quality, i- 1 * *- n is two p i an t studies were prompted by reports of 
the emission of formaldehyde vapors in confined areas under special 
conditions. 17 23 In effect, growth chambers or seeding magazines 
made of wood or particleboard were found to release formaldehyde that 
proved to be injurious to seeds or seedlings stored in them. These 
case histories one in the United States and the other in 
Australia were reported 25 yr apart. 

Finally, information on the response of plants to aldehydes has 
been uncovered as a result of the use of aldehyde-containing compounds 
in specific plant practices, such as postharvest treatment of fruit 
and the collection of maple syrup. 

It is the purpose of this chapter to assemble experimental data 
from these diverse sources related to the effect of aldehydes on 
vegetation. The material is critically reviewed with the intent of 

256 



257 

arriving at a definitive statement regarding the phytotoxicity of 
aldehydes. 

There is wisdom in the maxim that "those who cannot remember the 
past are condemned to repeat it." Before presenting information on 
aldehydes, a rather "new" group of pollutants, we should consider two 
models that have been painstakingly derived from studies of more 
thoroughly investigated pollutants, such as ozone, sulfur dioxide, and 
hydrogen fluoride. 

The first is a conceptual model of factors that influence the 
effects of air pollutants on vegetation (Figure 9-1) . This model was 
adapted from an evaluation of the phytotoxicity of ozone and 
photochemical oxidants. 16 The model shows that one must understand 
many factors before one can predict the response of a plant species to 
a specific pollutant. Those factors include genetic variability, 
stage of plant development, climatic and edaphic factors, interactions 
among pollutants, interactions among pathogens and insects, and 
pollutant dosage. Plant responses are classified as visible or subtle 
effects. 

In a second model, plant responses are classified according to the 
degree and type of effect produced at each level of biologic 
organization, and an attempt is made to relate effects at the cellular 
level with those anticipated at the level of the intact plant or plant 
community (Table 9-1) . This model was used by the National Research 
Council 15 to evaluate the effects of fluoride on vegetation. 



ALDEHYDE IN AMBIENT AIR AND PLANT INJURY 

The only report correlating aldehyde concentrations in ambient 
air with plant injury was published by Brennan et al. x In New 
Jersey, foliar symptoms in Snowstorm petunias (Petunia hybrida Vilma 
"Snowstorm") were similar to those reported by Taylor et al. in the 
field in California. 21 Leaves that were rapidly expanding in size 
appeared water soaked between the veins; and after several hours in 
sunlight, the upper leaf surfaces developed characteristic necrotic 
bands, and the lower leaf surfaces, a glazed appearance. The youngest 
leaves were marked only slightly, if at all, at the apex; and the 
oldest leaves escaped injury. (According to Stephens et al. , 2 
similar symptoms were experimentally induced in petunias with 
irradiated ozone-olefin mixtures, irradiated nitrogen dioxide and 
hydrocarbons, irradiated aldehydes, or peroxyacetylnitrate, PAN, which 
was common to all irradiated nitrogen oxide mixtures.) The appearance 
of symptoms could be correlated with increased concentrations of 
aldehyde in ambient air on either of the previous two 
days concentrations generally exceeding 0.20 ppm for 2 h or 0.30 ppm 
for 1 h by the bisulfite test. Inasmuch as the oxidant concentration 
in ambient air measured by a Mast sensor was lower than normal, the 
researchers assumed that neither peroxyacetylnitrate nor ozone was 
responsible for the injury to petunias. It was not established 
whether there was a causal relationship, rather than correlation, 
between aldehydes and plant damage. 



258 



NUMBER AND FREQUENCY 
OF EXPOSURES 



POLLUTANT 
CONCENTRATION 



DOSE 



PRESENCE OF 
OTHER POLLUTANTS 



DURATION OF 
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V 



CLIMATE 



SPECIES 



SOIL 



PLANT 
RECEPTOR ~= 



GENETIC 
VARIABILITY 



PATHOGENS 



AGE 



V 



MECHANISM OF ACTION 




EFFECTS 



VISIBLE 



SUBTLE 



FIGURE 9-1 Conceptual model of factors involved in air-pollution effects on 
vegetation. Adapted from National Research Council.-** 



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In a later paper, the New Jersey investigators reported that 6-14 
petunia-damaging episodes related to aldehydes occurred each year in 
the state over a 4-yr period. The white petunias were generally 
sensitive, the mixed white were intermediate, and the red, pink, 
purple, and blue tended to be resistant. 2 In 1978, Lewis and 
Brennan noted that the injury syndrome observed on petunias in the 
field could be reproduced with a mixture of ozone and sulfur dioxide 
in experimental fumigations. 12 



EXPERIMENTAL FUMIGATIONS 
VISIBLE PLANT INJURY CAUSED BY ALDEHYDES 

In an effort to simulate the plant injury observed in California 
as a result of so-called smog in the mid-1940s, Haagen-Smit ^t al. 8 
exposed five plant species that appeared to be the most sensitive in 
the field (spinach, endives, sugar beets, oats, and alfalfa) to a 
variety of organic and inorganic compounds in a fumigation chamber at 
concentrations generally less than 1 ppm. Several aldehydes were 
among the compounds tested. Formaldehyde had little effect on the 
test plants: exposure at 2 ppm for 2 h did not visibly affect any of 
the species, and exposure at 0.7 ppm for 5 h produced a symptom only 
in alfalfa (Table 9-2), and it was atypical. A 4-h exposure to 
trichloroacetaldehyde at 0.8 ppm caused smoglike symptoms on 
alfalfa speckled necrosis and marginal wilting of the leaves but did 
not, damage the other species. Exposure to the unsaturated aldehyde, 
acrolein, at 0.1 ppm for 9 h also produced symptoms on alfalfa 
resembling natural smog damage, but there was no suggestion of damage 
to the other species. Higher doses of acrolein (0.6 ppm for 3 h or 1.2 
ppm for 4.5 h) produced numerous sunken pits on both surfaces of 
spinach, endives, and beets, but the injury was unlike that observed 
in the field. Having failed to reproduce typical smog symptoms on 
four of the five sensitive plant species, the group of investigators 
in California concluded that aldehydes were not responsible for plant 
damage in the Los Angeles area. 

In 1960, Darley et al. 3 had occasion to evaluate acrolein 
effects on pinto beans as they were testing the phytotoxicity and 
eye-irritation severity of varius ozone-hydrocarbon mixtures. They 
reported damage to bean plants from exposures to acrolein at 2.0 ppm 
for 70 min that, "while not severe, was definite and indistinguishable 
from the underside bronzing typical of oxidant damage." It should be 
noted that from 1940 to 1960 the term "oxidant damage" was used to 
describe under-surface leaf injury that was later proved to be caused 
by PAN. 

, A more recent study by N. Masaru and K. Fukaya (personal 
communication) indicated a greater phytotoxicity of acrolein than 
previously reported. Experiments in Japan revealed that bean leaves 
exposed to acrolein at 0.5 ppm developed brown foliar lesions after 4 
h, and morning-glories developed similar symptoms after 6-7 h. Damage 
was more severe if the plants were fumigated in wet, rather than dry, 



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262 

conditions. Radish leaves did not respond until the acrolein exposure 
was increased to 6-7 h at 1.5 ppm, and neither geraniums nor tomato 
plants were affected even at the greater exposure. Thus, Masaru and 
Fukaya demonstrated two principles that have been apparent when air 
pollutants have been studied more extensively: species respond 
differently to a given exposure to pollutant, and environmental 
factors affect plant response. 



VISIBLE PLANT INJURY CAUSED BY IRRADIATED ALDEHYDES 

While the California group was considering an ozone-olefin 
reaction as the probable source of eye irritation and plant damage, 
Stephens _et al. l9 recognized that aldehydes were products of such 
reactions. They irradiated selected aldehydes in static systems with 
48 Blacklite fluorescent tubes that emitted radiation of wavelength 
less than 3000 A. They then passed the aldehydes and their reaction 
products over petunias and pinto bean leaves (8 or 14 d old) for 1-1.5 
h (Table 9-3). The concentrations of aldehydes were 4.5-9.0 ppm at 
the start of the fumigation and decreased to 1.5-4.5 ppm by the end of 
the fumigation. Formaldehyde and acetaldehyde and their reaction 
products caused little or no injury to the plants. Propionaldehyde 
and butyraldehyde and their reaction products produced a glazing of 
the lower surface of petunia leaves and of trifoliate and 8-d old 
primary leaves of pinto beans, but did not injure 14-d old primary 
leaves of the beans. Irradiated ozone-olefin mixtures or irradiated 
nitrogen dioxide-hydrocarbon mixtures caused a similar response. 

Speculating that small concentrations of nitrogen oxides may have 
been present in the Stephens ejt al. fumigation, Hindawi and 
Altshuller 9 investigated the phytotoxicity of irradiated 
formaldehyde and propionaldehyde in the presence of low and high 
concentrations of NO X (Table 9-4). The species that they tested 
(petunias, tobacco, and pinto beans) were not affected by a 
combination of formaldehyde at 6.1 ppm and NO X at 0.9 ppm for 4 h, 
despite the generation of oxidant at 0.65 ppm. They speculated that 
the oxidant was not ozone, but a nontoxic compound. The next higher 
homologue, propionaldehyde, proved more toxic, causing injury to 
plants at 0.52 ppm in the presence of NOx at 0.5 ppm. On the basis 
of symptom type and species of plant affected, the researchers 
identified the same five classes of injury that they had observed in 
the same three plant species exposed to irradiated automobile 
exhaust, in discussing the aldehydes, they expressed an opinion that 
irradiated acetaldehyde did not cause significant damage, inasmuch as 
Stephens et al. had observed no phytotoxicity with a mixture of 
irradiated cis-2-butene and ozone, despite a high yield of 
acetaldehyde. They also assumed that acrolein did not cause 
significant damage to petunias, pinto beans, and tobacco leaves, 
because there was no phytotoxicity in their own experiments with 
irradiated mixtures of 1,3-butadiene and nitrogen oxide, although 
acrolein at 1.0 ppm was formed as a product, it cannot be assumed, 



263 

TABLE 9-3 
Plant Damage Caused by Four Irradiated Aldehydes 



Concentration of 
Aldehydes, ppm 

A B C D 



Duration of 
Fumigation, h 



Plant Injury 
14-d-old 8-d-old 
Pinto 



17.7 15.8 8.5 

17.9 16.0 8.3 2.8 

14.6 13.8 6.9 3.8 

12.5 11.8 6.3 2.5 

17.5 16.5 8.2 4.5 

22.0 21.4 9.0 3.6 

11.2 10.6 5.1 1.7 

16.0 12.0 6.5 1.5 

14.4 8.9 4.5 1.6 



Pinto Pinto Petunia 
Butyraldehyde 

1.5 Severe Severe 

1 Severe Severe 

Propionaldehyde 

1.25 Severe Severe 

1 Severe Severe 

Acetaldehyde 

100 Light 

1 00 

1.5 Light Light 

Formaldehyde 

0.25 Atypical 

1 Atypical 



19 
Reprinted with permission from Stephens et al. 

b A, in cell before irradiation; B, in cell after 2 h of irradiation with 
black lights in static system; C, at beginning of plant fumigation, 
after circulation through plant box; D, at end of fumigation. 







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265 

however, that the phytotoxicity of an aldehyde in a complex mixture is 
the same as when it occurs singly. 



SUBTLE PLANT INJURY CAUSED BY ALDEHYDES 

In addition to the investigations involving visible effects of 
aldehydes on plants, there has been some experimental work on their 
physiologic effects. Among the processes examined have been 
photosynthesis, respiration, transpiration, and pollen germination. 



Photosynthesis and Respiration 

Researchers in Canada 1 * evaluated the effect of formaldehyde on 
photosynthesis of an alga, Euglena gracilis. When they passed air 
containing formaldehyde at 0.075 ppm through a 5-ml sample of euglena 
in bicarbonate buffer for 1 h, the rates of photosynthesis and 
respiration of the cells were slightly but not statistically 
significantly reduced (Table 9-5). In fasted cells (those suspended 
in buffer for 4.5 h before aldehyde exposure) the researchers noted 
that formaldehyde might even have a beneficial effect. Propionaldehyde 
at 0.100 ppm decreased the rates of photosynthesis and respiration of 
euglena; again, fasting of the cells offered protection against the 
toxic effects (Table 9-5) . 

The notion that formaldehyde may be beneficial to algae is 
consistent with the results of studies by Doman et al. 5 and Krall 
and Tolbert, 11 who demonstrated that [ C] formaldehyde was 
absorbed by leaves of kidney bean and barley plants and that in light 
it was fixed rapidly in products similar to those formed from carbon 
dioxide. 



Transpiration 

The effect of aldehydes on transpiration was evaluated by Fries et 
al. 7 of Sweden. Having observed in a prior investigation that 
ethereal oils in gaseous form reduced transpiration rates in leaves, 
they proceeded to try to determine whether specific aldehydes were 
responsible. They enclosed wheat seedlings in a cuvette through which 
air containing a specific aliphatic aldehyde was passed for 1 h at a 
constant flow rate, temperature, and relative humidity. All six 
aliphatic aldehydes tested (trans-2-hexenal, pentanal, hexanal, 
heptanal, octanal, and nonanal) at 1.0 yM (24 ppm) caused a decrease 
in transpiration rate. Because the aldehyde treatment caused a 
reduction in transpiration rate even greater than that caused by 
complete darkness, there was some question whether the change was due 
entirely to stomatal closure. Irrespective of the mechanism, Fries et 
al. concluded that volatile aldehydes may play a role in the control 
of transpiration of plants under field conditions. It would be 



266 



TABLE 9-5 

Effect of Exposure to Formaldehyde (at 0.075 ppm for 1 h) and 

Propionaldehyde (at 0.100 ppm for 1 h) on Rates of Photosynthesis 

and Respiration of Euglena gracilis a 

Rate b 

Formaldehyde Propionaldehyde 

Control Exposure Control Exposure 

Unfasted cells 

Photosynthesis 5.25 4.54 6.09 4.71 

Respiration 2.26 1.83 2,18 1.85 

Fasted cells 

Photosynthesis 4.22 4.61 5.25 5.45 

Respiration 1.47 1.54 1.75 1.66 

a Reprinted with permission from deKoning and Jegier.^ 

b For photosynthesis, micromoles of oxygen given off by 6.3 x 10 6 cells 
in 10 min; for respiration, micromoles of oxygen absorbed by 6.3 x 10^ 
cells in 10 min. 



267 

important to know whether the effect persisted after the removal of 
the pollutant. 



Pollen Germination 

Pollen germination has proved sensitive to various air pollutants, 
such as ozone. 6 The implication is that the inhibition of pollen 
germination will be reflected as an adverse effect on reproductive 
capacity of a species. In 1976, Masaru et al. 13 reported on their 
examination of the effects of formaldehyde, acrolein, sulfur dioxide, 
nitrogen dioxide, and ozone on lily pollen. They sowed pollen grains 
on culture medium, placed the medium in a fumigation chamber with 
pollutants at various concentrations, and measured pollen tube length 
after 24 h (Table 9-6). A 5-h exposure to formaldehyde at 0.37 ppm 
resulted in a significant reduction in pollen-tube length, whereas a 
1- or 2-h exposure was innocuous. When formaldehyde was increased to 
2.4 ppm, a 1-h exposure caused a decrease in tube length. The 
investigators observed that, with respect to pollen, the activity of 
formaldehyde was comparable with that of nitrogen dioxide. Acrolein 
proved to be more injurious to pollen than any of the other pollutants 
tested. At 0.40 ppm, acrolein caused a 40% decrease in pollen-tube 
elongation after 2 h; at 1.70 ppm, it completely prevented extension 
of the pollen tube. Having previously observed that exposure to 
acrolein at 0.50 ppm for 6-7 h caused acute foliar injury to lily, 
Masaru et^ al.. 13 concluded that lily pollen was as sensitive as 
foliage to aldehyde treatment. Masaru et_ al. also tested combinations 
of pollutants on lily pollen. Pollen grains exposed to sulfur dioxide 
at 0.69 ppm for 30 min or to nitrogen dioxide at 0.15 ppm for 30 or 60 
min showed little inhibition of tube elongation; if they were then 
exposed to formaldehyde at 0.26 ppm, significant inhibition occurred 
(Table 9-7). 



PLANT EXPOSURES TO ALDEHYDES UNDER SPECIAL CONDITIONS 
WOODEN CONTAINERS 

Two reports of aldehyde damage to seedlings arose from similar 
circumstances in the United States and Australia some 25 yr apart. 
While culturing oat seedlings in a growth chamber made of ponderosa 
pine and hardboard (Masonite Tempered Presdwood) , Weintraub and 
Price 23 observed a marked retardation of seedling growth. Other 
species including wheat, corn, sorghum, barley, tomato, bean, 
lettuce, and radish were similarly affected. Hypothesizing that a 
toxic agent was liberated from the box, they confined seeds under a 
bell jar with small pieces of well-seasoned pine board or with 
hardboard and again observed the inhibitory action. Nine other species 
of wood were associated with the same effects. In an attempt to 
identify the volatile compound, they placed vials of various compounds 
in a desiccator containing oat seeds. The most inhibitory compounds 



268 
TABLE 9-6 

Pollen-Tube Length of Lilium longiflorum after Exposure of 
Pollen Grains to Various Pollutants a 



Pollutant Gas 
Sulfur dioxide 



Nitrogen dioxide 



Ozone 



Formaldehyde 



Acrolein 



Pollutant 

Concentration, 

ppm 



Pollen-Tube Length, % of 
control, after Exposure 
Lasting: 





1 h 


2 h 


5 h 


0.40 


96.2 


92.4 


0.0 


0.71 


45.0 


21.2 


0.0 


2.50 


32.2 


0.0 


0.0 


0.57 


89.2 


85.7 


80.0 


1.70 


77.5 


60.3 


17.2 


2.00 


31.7 


0.0 


0.0 


0.28 


81.8 


80.0 


72.7 


2.09 


88.2 


95.5 


80.0 


0.37 


100.0 


100.0 


27.7 


1.40 


86.5 


67.3 


0.0 


2.40 


62.5 


41.6 


0.0 


0.40 


90.0 


40.0 


0.0 


1.40 


44.4 


0.0 


0.0 


1.70 


0.0 


0.0 


0.0 



a Reprinted with permission from Masaru e_t al, 



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269 



270 

proved to be acrolein, crotonaldehyde, hydrogen peroxide, crotonic 
acid, and acrylic acid. Concentrations of the compounds were not 
determined. 

About 25 yr later, wheat-breeders experienced a similar problem in 
using a magazine planting device made of bonded particleboard. If 
seeds were stored in such a magazine for 1-3 d, the germination 
percentage was reduced; if stored for 3 wk, the seeds completely fail 
to germinate. 17 The authors suspected that free formaldehyde 
released from the bonding resin of the particleboard was responsible 
for the problem. They conducted a series of experiments with wheat in 
contact with or at various distances from particleboard bonded with 
urea-f ormaldehyde . After 1 d in a seeding magazine, the emergence 
rate for seedlings started to decline; after 1.5 d, there was only 3% 
emergence. If wheat seeds were stored in a paper bag at various 
heights above the particleboard for 30 mo, all seeds within 7.5 cm of 
the board were adversely affected. If the particleboard was cured for 
5 d at 40C, the volatile substance was no longer released, and seeds 
were not affected. The authors recommended that bonded particleboard 
not be used in the construction of seeding magazines. 



POSTHARVEST TREATMENTS 

The literature of plant pathology contains information on two uses 
of aldehydes that provide additional data on plant effects. 
Acetaldehyde vapor at concentrations far in excess of ambient 
exposures has been used to prevent postharvest decay of strawberries 
caused by Botrytis cinerea and Rhizopus stolonifer . 18 Exposure to 
1% acetaldehyde vapor prevented decay and had no adverse effect on 
quality (as indicated by total solids and pH) of the berries. Exposure 
to 4% acetaldehyde produced objectionable results, decreasing the 
quality and injuring the caps of the berries. 



MAPLE-SYRUP COLLECTION 

Paraf ormaldehyde pills have been used on tapholes drilled into 
sugar maple trees to increase or prolong the yield of sap. 
Apparently, par af ormaldehyde temporarily inhibits the growth of 
microorganisms in the taphole that would normally restrict sap flow. 
Walters and Shigo 22 studied the long-range effect of such 
treatment. They treated some 200 mature sugar maple trees with a 
250-mg paraformaldehyde pill for 2 mo and harvested selected trees 
over a 35-mo period. They found a higher incidence of discolored or 
decayed wood in the treated trees than in the controls. 
Paraformaldehyde altered the vascular and ray systems that play an 
important role in vessel plugging of trees and thereby facilitated 
invasion by wood-decaying fungi. 



271 
DISCUSSION 

To what extent does the information on aldehydes satisfy the two 
models (Figure 9-1 and Table 9-1) and approximate the impact of this 
class of pollutants on vegetation? Inspection of Figure 9-1 reveals 
that a cluster of factors related to the plant receptor and another 
cluster related to pollutant dosage determine the nature and degree of 
plant response likely to be elicited by a given pollutant. 

With regard to the factors influencing the plant receptor, 
investigations involving air pollutants, such as ozone and fluoride, 
have emphasized that genetic makeup is foremost in determining the 
sensitivity or tolerance of a plant. Well over 100 plant species, as 
well as many groups of cultivars of some 20 species have been tested 
for their reactions to ozone and fluoride, and lists of plants that 
are highly sensitive, of intermediate or slight sensitivity, or 
resistant to each pollutant have been compiled. In contrast, only 15 
species have been tested for sensitivity to aldehydes; the only 
results on intraspecif ic variations were those related to petunias in 
the ambient-air study conducted in New Jersey. 

In addition to the genetic component, the stage of plant 
development influences the response of a plant receptor. Most 
frequently, it is the vegetative parts, rather than the fruit or 
floral parts, that exhibit toxicity symptoms, although there are 
exceptions, such as peach fruit injury due to fluoride. The age of 
the tissue is critical. For example, plants at an age associated with 
nearly complete expansion of leaves are at their peak of ozone 
sensitivity, but are past their peak of PAN sensitivity. The stage of 
maximal sensitivity to aldehydes has not been determined, although 
there is a clue in the greater susceptibility of young bean leaves 
than of old leaves. Many species must be tested to determine the part 
of their life cycle when injury is most likely. 

The sensitivity of a plant receptor is also influenced by many 
climatic and edaphic factors. Some of the climatic factors that have 
been important with respect to more thoroughly investigated air 
pollutants are temperature, relative humidity, light quality and 
intensity, photoperiod, and rate of air movement. None of these has 
been systematically evaluated in aldehyde fumigations. Masaru et a^. , 
however, did observe that wet leaves were injured more than dry 
leaves. Among the edaphic factors that influence the growth and 
development of the plant receptor and hence the response to a 
pollutant are soil moisture, aeration, and nutrients. None of these 
has been evaluated in aldehyde studies. 

Finally, biotic factors have been found to alter a plant 
receptor. Research with ozone has demonstrated that the presence of a 
pathogen in a plant may increase or decrease ozone phytotoxicity. 
Information of this nature on aldehydes is lacking. 

Turning from the factors that act directly on the receptor, it is 
necessary to consider the factors that are involved in the dose 
component. According to Figure 9-1, pollutant concentration, duration 
of exposure, and number of exposures are important. Obviously, a high 
dose of pollutant is more apt to be injurious than a low dose. 



272 

Although it is not self-evident, it may also be true for some 
aldehydes, as it is for ozone, that a given dose applied over a short 
period produces a greater plant reponse than the same dose applied 
over a long period. An acute exposure may, in fact, evoke a response 
different from that to a chronic exposure, depending on the mechanism 
of action of the pollutant and the mechanism of resistance of the 
plant. In aldehyde research, excluding the work with particleboard 
containers, exposures have been short (1-6 h) . Concentrations of 
aldehydes used with higher plants generally have ranged from 0.2 to 
2.0 ppm. Because the investigators used analytic techniques of varied 
sensitivity and precision for measuring aldehydes (Table 9-8), it is 
futile to attempt to compare their results. (Methods for aldehyde 
determination are presented in Chapter 6) . Indeed, whether the 
concentrations used in experimental work are realistic, with respect 
to those occurring in ambient air, will not be known until there is a 
refined standard method for use in experimental and ambient 
atmospheres. In a sense, history would be repeating itself, in that 
methods for ozone (oxidant) determination have progressed through a 
series of "acceptable" techniques since the toxicity of ozone was 
first recognized. Even assuming the availability of better analytic 
techniques, one must recognize that aldehydes are present in complex 
mixtures with other pollutants that may also be phytotoxic and 
interact with the aldehydes. In 1966, Menser and Heggestad 111 
established that administration of mixtures of sulfur dioxide (0.50 
ppm) and ozone (0.03 ppm) for 2 h caused 23% foliar injury on tobacco, 
whereas administration of the gases separately produced no injury. 
This type of experimentation has not been done with aldehydes, except 
that of Masaru et al_. , 13 who observed that exposure to sulfur 
dioxide or nitrogen dioxide, followed by exposure to formaldehyde, 
resulted in greater inhibition of pollen germination than did 
exposoure to either pollutant singly. Exposure to formaldehyde after 
ozone exposure appears to decrease pollen-tube length, but the 
differences were not significant. 

Inspection of the second model reveals the need for assessing 
air-pollution effects on plants at many levels of biologic 
organization, including cell, tissue, organism, and ecosystem. 
Ideally, one would know whether any of the structural or functional 
alterations initiated at the cellular level are expressed at any of 
the higher levels. For example, are the changes in rates of 
photosynthesis and respiration responsible for foliar lesions in an 
intact leaf? Does the presence of a necrotic or chlorotic lesion have 
an important effect on the plant in toto? Is growth or yield 
reduced? Does injury to individual plants constitute a threat to the 
ecosystem? These questions cannot yet be answered with respect to 
the aldehydes the available information is too sparse. 



273 



TABLE 9-8 
Analytic Methods for Aldehydes Used in Plant Studies 



Compound 

Aldehydes (including 
acrolein) 

Acrolein 



Acrolein 

Aldehydes 
Aldehydes 
Formaldehyde 

Formaldehyde, 
propionaldehyde 



Method 

Gravimetric precipitation of dimedons 
or 2,4-dinitrophenyl hydrazones 

Absorption in buffered semicarbazide 
hydro chloride solution and reading on 
s pec tropho tome ter 

Absorption in 0.1 N hydroxylamine 
hydrochloride solution and measurement 
by m-aminophenol method 

Bisulfite addition 
Long-path infrared cell 
Chromotropic acid 

3-Methyl-2-benzothiazolone hydrazone 
test 



Reference 
8 



13 

1 

21 
13 

4 



274 
REFERENCES 

1. Brennan, E. f I. A. Leone, and R. H. Dames. Atmospheric aldehydes 
related to petunia leaf damage. Science 143:818-820, 1964. 

2. Brennan, E. , I. A. Leone, R. H. Daines, and A. Mitlehner. 
Polluted petunias. Florists' Rev. 139 (3599) :29, 75-76, 1966. 

3. Darley, E. P., J. T. Middle ton, and M. J. Garber. Plant damage 
and eye irritation from ozone-hydrocarbon reactions. Agric. Food 
Chem. 8:483-485, 1960. 

4. deKoning, H., and Z. Jegier. Effect of aldehydes on 
photosynthesis and respiration of Euglena gracilis. Arch. 
Environ. Health 20:720-722, 1976. 

5. Doman, N. G. , A. K. Romanova, and Z. A. Terent'eva. Conversion of 
some volatile organic substances absorbed by leaves from the 
atmosphere. Doklady Akad. Nauk S.S.S.R. 138:702, 1961. (in 
Russian) 

6. Feder, W. A. Reduction in tobacco pollen germination and tube 
elongation, induced by low levels of ozone. Science 160:1122, 
1968. 

7. Fries, N., K. Flodin, J. Bjurman, and J. Parsby. Influence of 
volatile aldehydes and terpenoids on the transpiration of wheat. 
Naturwissenschaften (Berlin) 61:452-453, 1974. 

8. Haagen-Smit, A. J., E. F. Darley, M. Zaitlin, H. Hull, and W. M. 
Noble. Investigation on injury to plants from air pollution in 
the Los Angeles area. Plant Physiol. 27:18-34, 1952. 

9. Hindawi, I. J., and A. P. Altshuller. Plant damage caused by 
irradiation of aldehydes. Science 146:540-542, 1964. 

10. Kostychev, S. P. Chemical Plant Physiology. Philadelphia: P. 
Blakiston's Sons and Co., 1931. 354 pp. 

11. Krall, A. R., and N. E. Tolbert. A comparison of the light 
dependent metabolism of carbon monoxide by barley leaves with that 
of formaldehyde, formate and carbon dioxide. Plant Physiol. 
32:321-326, 1957. 

12. Lewis, E., and E. Brennan. Ozone and sulfur dioxide mixtures 
cause a PAN-type injury to petunia. Phytopathology 68:1011-1014, 
1978. 

13. Masaru, N. , F. Syozo, and K. Saburo. Effects of exposure to 
various injurious gases on germination of lily pollen. Environ. 
Pollut. 11:181-187, 1976. 

14. Menser, H. A., and H. E. Heggestad. Ozone and sulfur dioxide 
synergism: Injury to tobacco plants. Science 153:424-425, 1966. 

15. National Research Council, Committee on Biologic Effects of 
Atmospheric Pollutants. Effects of fluoride on vegetation, pp. 
77-133. In Fluorides. Washington, D.C.: National Academy of 
Sciences, 1971. 

16. National Research Council, Committee on Medical and Biologic 
Effects of Environmental Pollutants. Plants and microorganisms, 
pp. 437-585. In Ozone and Other Photochemical Oxidants. 
Washington, D.C.: National Academy of Sciences, 1977. 

17. O'Brien, L., and R. A. Orth. An unexpected cause of poor 
germination and emergence of wheat. Crop Sci. 18:510-512, 1978. 



275 

18. Prasad, K. f and G. J. Stadelbacher . Effect of acetaldehyde vapor 
on postharvest decay and market quality of fresh strawberries. 
Phytopathology 64:948-951, 1974. 

19. Stephens, E. R. , E. F. Darley, and 0. C. Taylor. Air Pollution 
Research at University of California, Riverside. An Interim 
Report on the Cooperative Program between William E. Scott and 
Associates, Perkasie, Pa., and the University of California, 
Riverside. Prepared for meeting of Research Advisory Committee 
Smoke and Fumes Committee, American Petroleum Institute, held at 
Riverside, California, October 1-2, 1959. 

20. Stephens, E. R. , E.F. Darley, 0. C. Taylor, and W. E. Scott. 
Photochemical reaction products in air pollution. Int. J. Air 
Water Pollut. 4:79-100, 1961. 

21. Taylor, O. C., E. R. Stephens, E. F. Darley, and E. A. Cardiff. 
Effect of air-borne oxidants on leaves of the pinto bean and 
petunia. Proc. Amer. Soc. Hort. Sci. 75:434-444, 1960. 

22. Walters, R. S., and A. L. Shigo. Discolouration and decay 
associated with paraformaldehyde-treated tapholes in sugar maple. 
Can. J. Forest Res. 8:54-60, 1978. 

23. Weintraub, R. L., and L. Price. Inhibition of plant growth by 
emanations from oils, varnishes, and woods. Smithson. Misc. 
Collect. 107(17) :1-13, 1948. 



CHAPTER 10 
EFFECTS OF ALDEHYDES ON AQUATIC ORGANISMS 



This chapter presents an overview of current knowledge of the 
effects of aldehydes on aquatic organisms. It addresses 39 aldehydes , 
which were considered to be potentially more hazardous to aquatic life 
than other aldehydes by having been identified in water, having been 
produced or consumed in the United States in amounts of at least 1 
million pounds per year, having been used as pesticides, or being 
currently considered by EPA as high-priority water pollutants. These 
aldehydes are listed in Table 10-1. 

Of the 39 aldehydes, 36 have been identified in water, including 
industrial and sewage-treatment plant discharges, surface waters, and 
drinking water (see Chapter 5); the 36 comprise 10 of the 11 
high-production or high-consumption aldehydes and all the pesticide 
aldehydes except metaldehyde. Only two aldehydes acrolein and endrin 
aldehyde are currently considered by EPA to be high-priority water 
pollutants. The reason for so classifying endrin aldehyde is unclear; 
it may be a transformation product of the pesticide endrin. 



TOXIC ITY TO AQUATIC ORGANISMS 

Very little is known about the toxicity of most of these 
potentially hazardous aldehydes to aquatic organisms. Eighteen have 
been evaluated for toxicity, but only one has been evaluated for 
chronic toxicity and bioconcentration potential. Median tolerance 
limits (e.g., LC 5 QS and ECsos) have been reported for seven; the 
remaining 11 have been evaluated only for selective piscicidal 
activity. 



ACROLEIN 

Of all the aldehydes that have been evaluated for toxicity to 
aquatic organisms, acrolein is the most toxic. For fish, the LC$Q 
for exposure periods of 24-144 h ranges from 0.046 to 0.24 ppm (Table 
10-2) . Aquatic invertebrates appear to be as sensitive as fish. 
Butler 7 estimated the 48-h LCso for a marine shrimp (Penaeus 
azteca) to be 0.1 ppm. He also estimated that exposure at 0.055 ppm 
for 96 h would reduce the growth rate of oysters (Crassostrea 

276 



277 

TABLE 10-1 
Aldehydes Potentially Hazardous to Aquatic Organisms 



Identified 
in Water 3 

X (ESD) 
X (ESD) 
X (ES) 
X (ESD) 
X (ESD) 
X (S) 
X (SD) 
X (S) 
X (D) 
X (SD) 

X (D) 
X (S) 

X (S) 
X (SD) 
X (SD) 

X (D) 
X (S) 
X (E) 
X (ED) 
X (D) 
X (D) 
X (ED) 
X (S) 
X (D) 

X (ESD) 
X (D) 
X (S) 
X (ESD) 
X (D) 
X (E) 
X (E) 
X (E) 
X (S) 
X (D) 
X (ES) 
X (E) 



High Pro- 
duction or 
Consumption 

X 
X 
X 
X 
X 



Pesti- 
cide 

X 
X 



Aldehyde 

Acetaldehyde 

Acrolein b 

Anisaldehyde 

Benzaldehyde 

Butyraldehyde 

Capraldehyde 

Caproaldehyde 

Caprylaldehyde 

Chloral b 

Cinnamaldehyde 

Citronellal 

Crotonaldehyde 

Di~tert-butylhydroxy- 

4-benzaldehyde 
Dichlorobenzaldehyde 
Dimethylbenzaldehyde 
Enanthaldehyde b 
Endrin aldehyde 
2-Ethylbutyraldehyde 
2-Ethylcaproaldehyde 
Formaldehyde 
Furaldehyde b 
Isobutyr aldehyde 
Isopropionaldehyde 
Isovaleraldehyde 
Mesitaldehyde 
Me thacrolein b 
Met aldehyde 

2-Methylpropionaldehyde 
3-Me thyl valeraldehyde 
Nonylaldehyde 
Par aldehyde 
Propionaldehyde b 
Sallcylaldehyde b 
Sorbaldehyde 
Syringaldehyde 
Undecylaldehyde 
Valeraldehyde 
Vanillin 5 
Veratraldehyde b 

a E industrial or sewage treatment plant effluent; S = surface water; 
D = drinking water. 

b Evaluated for toxicity. 



LPA 

Priority 

Pollutant 



278 



TABLE 10-2 
Acute Toxicity of Acrolein to Fish 

Exposure 
Species LC qn , ppm Time, h Reference 

Oncorhynchus tschawytscha 0.08 24 5 

(king salmon) 

Salmo gairdnerii 0.065 24 5 

(rainbow trout) 

Salmo trutta 0.046 24 6 

(brown trout) 

Lepomis macrochirus 0.10 96 19 

(bluegill sunfish) 

Micropterus salmoides 0.16 96 19 

(largemouth bass) 

Amia calva 0.062 24 19 

(bowfin) 

Pimephales promelas 0.084 144 20 

(fathead minnow) 

Gambusia af finis 0.061 48 19 

(mosquito fish) 

Fundulis similis 0.24 48 7 

(longnose killifish) 



279 

virginica) by 50%. For the water flea (Daphnia magna), Macek and 
co-workers 20 reported a 48-h LC5Q of 0.057 mg/L. 

Studies by the Shell Development Company l have shown acrolein 
to be lethal to various aquatic flora such as Hydrodictyon sp., 
Spirogyra sp. , Potomogeton sp. , Zannichellia sp. , Cladophera sp., and 
Ceratophyllum sp. at concentrations ranging from 1.5 to 7.5 ppm. 

Macek and co-workers 20 evaluated acrolein for chronic effects in 
the water flea (p_. magna) and the fathead minnow (Pimephales promelas) 
with the flow-through exposure technique, which provides for 
continuous replacement of the test solutions in the exposure tanks. 
They also based their toxicity estimates on measured acrolein 
concentrations. The water flea was exposed at five concentrations, 
from 0.0032 to 0.043 mg/L, for 64 d (three generations). Although the 
compound had no statistically significant effect on fecundity at the 
concentrations tested, it significantly reduced survival at 0.034 and 
.043 mg/L. 

In the chronic test with minnows, the test concentrations ranged 
from 0.0046 to 0.042 mg/L, and the test was begun with 27-d-old fish. 
None of the tested concentrations affected the growth, survival, or 
reproductive capacity of these fish; however, at 0.042 mg/L, the 
compound significantly reduced the survival of their offspring. 

The EPA has determined that acrolein has acute and chronic toxic 
effects on freshwater aquatic organisms at concentrations as low as 
0.068 and 0.021 mg/L, respectively, and acute toxic effects on marine 
organisms down to 0.055 mg/L. 32 There are no data on chronic 
toxicity in sensitive marine organisms. Toxic effects would occur at 
lower concentrations among species that are more sensitive than those 
tested. 



FORMALDEHYDE 

Kitchens and co-workers 18 reviewed all the available published 
information on formaldehyde as an environmental pollutant. They 
discussed the structure and chemical and physical properties of 
formaldehyde, its production and uses, the sources of environmental 
formaldehyde, monitoring and analytic methods, and its human health 
and environmental effects. Much of the aquatic toxicologic 
information presented by Kitchens and associates was from a review by 
Schnick 30 of the toxicity of formalin. 

Formalin has been evaluated for acute toxicity with a variety of 
fish, amphibians, invertebrates, and algae. Schnick 's review 30 
presented LC 50 s for 20 freshwater and marine fish. A comparison of 
the 24-h LC 50 s (the most common reported) showed striped bass 
(Morone saxitalis) to be the most sensitive of the fish tested. The 
24-h LC 50 of formalin for that species was 10-30 yl/L (3.7-11.1 
mg/L as formaldehyde). Young fish were more sensitive than older 
fish. For the other species tested, the 24-h LC 50 s ranged from 
about 50 to 120 rag/L as formaldehyde. 

Formalin is probably the most widely used agent for treating fish 
for ectoparasitic infections and fish eggs for fungal infections. 33 
Treatment is usually very short, but frequently repetitive. The 



280 

recommended concentration for treating ectoparasitic infections is 
formaldehyde at about 160-250 mg/L applied in the water for 1 h/d for 
up to 3 d. With fish reared in ponds, formalin is added to the pond to 
achieve a formaldehyde concentration of 5-9 mg/L and permitted to 
dissipate naturally. To treat eggs with fungal infections, much 
higher concentrations are used (about 620 mg/L); however, the exposure 
period is reduced to 15 min/d. These treatment schedules indicate that 
fish and fish eggs can tolerate concentrations considerably higher 
than the 24-h LCsQS, but for only short periods. 

In bullfrog tadpoles exposed to formalin at 275-325 yl/L (about 
100-120 mg/L as formaldehyde) for 48 h, 20-30% mortality has been 
reported; ll * however, 100% mortality has been observed in bullfrog 
tadpoles exposed for 72 h to formalin at as low as 40 yl/L (15 mg/L 
as formaldehyde) and in tadpoles of the leopard frog (Rana pipiens) 
and toad (Bufo sp.) exposed at 30 and 50 yl/L (11 and 18.5 mg/L as 
formaldehyde), respectively. ** l "* * 7 At a concentration of 100 
yl/L (37 mg/L as formaldehyde) , formalin was not toxic to larvae of 
the salamander, Amblystoma tigrinum in 72 h. 11 * In toxicity tests 
with the freshwater invertebrate Daphnia magna, mortality occurred at 
formalin concentrations as low as 13.5 yl/L (5 mg/L as 
formaldehyde). 26 In a review by McKee and Wolf, 23 the median 
threshold concentration for formaldehyde was reported to be 2 mg/L for 
Daphnia sp. (2-d exposure). Helms lk reported observing no effect in 
crayfish (Procambarus blandingi) exposed to formalin at up to 100 
yl/L for up to 72 h. 

Gellman 1 2 estimated the toxic concentration of formaldehyde for 
aerobic aquatic microorganisms to be between 130 and 175 mg/L, and 
Hermann 15 found that 740 mg/L inhibited their oxygen utilization by 
50%. 

Helms 11 * observed no effect in the aquatic algae Aphanothece sp., 
Oscillatoria sp. f and Rhizoclonium sp. exposed for 7 d to formalin at 
up to 100 yl/L (37 mg/L as formaldehyde). However, cultures of 
Scenedesmus sp., Sirogonium sp., Spyrogyra sp., and Stigeoclonium sp. 
did not survive at concentrations of 15 yl/L (5.6 mg/L as 
formaldehyde) or higher. Euglena gracilis, exposed to formaldehyde at 
0.075 ppm for 1 h, showed reduced photosynthesis and respiration, 16 
but the reduction in photosynthesis was not statistically significant. 



OTHER ALDEHYDES 

Table 10-3 presents acute-toxicity estimates reported for 
acetaldehyde in two species of fish, a shrimp, and two species of 
algae. Unpublished studies performed by the Dow Chemical Company 
(R.J. Moolenau, personal communication) on acetaldehyde showed 70 ppm 
to be lethal to fathead minnows (Pimephales promelas) in 96 h; 
however, exposure for 96 h at 60 ppm caused no toxic effect. 
Acetaldehyde thus appears to be acutely lethal over a very narrow 
concentration range. 

For furaldehyde, Middlebrooks and co-workers, 21 * using the 
harlequin fish (Rasbora heteromorpha) , determined the 24- and 48-h 



281 



TABLE 10-3 
Acute Toxicity of Acetaldehyde to Acquatic Organism 

Concentration, 
Species Statistic mg/L Reference 

Lagodon rhomboides 24-h LC^Q 70 11 

(pinfish) 

Lepomis macrochirus 9b-h LC^Q 53 8 

(bluegill sunfish) 

Crangon crangon 24-h LC^Q >100 29 

(shrimp) 

Nitzchia linearis 5-d EC 5Q (growth) 237 1 

(alga) 

Navicula seminulum EC 5Q (growth) 239 28 

(alga) 



282 

LC5QS to be 31 and 23 ppm, respectively. Mattson and co-workers 22 
reported a 96-h LC 50 of 32 ppm for the fathead minnow (P. 
promelas) . With the bluegill sunfish (L. macrochirus), Turnbull and 
co-workers 31 determined the 24- and 48-h ^598 of furaldehyde to 
be 32 and 24 mg/L, respectively. In very turbid water, the 24-h 
LC5Q for bluegills has been reported as 44 mg/L, and the 48- and 
96-h LC 50 s both have been determined to be 24 mg/L. 31 * The 
lowest reported 96-h LC 50 of furaldehyde is 1.2 ppm, 35 for 
bluegills. 

Dawson and co-workers 9 tested crotonaldehyde and propionaldehyde 
with bluegill sunfish (L. macrochirus) and tidewater silversides 
(Menidia beryllina) . The 96-h LCsQS of crotonaldehyde for the 
bluegill and silversides were 3.5 and 1.3 mg/L, respectively. The 
96-h LC5QS of propionaldehyde were 130 mg/L for the bluegill and 100 
mg/L for the silversides. 

According to Mattson and co-workers, 22 the 96-h 1^59 of 
vanillin for fathead minnows is 112-121 mg/L, on the basis of two 
tests. Palmer and Maloney 27 determined the toxicity of vanillin to 
six species of algae with concentrations up to 2 mg/L. This 
concentration slightly inhibited the growth of Gomphonema sp., but had 
no effect on the other species. In a search for a chemical agent that 
would selectively kill the Oregon squawfish (Ptychocheilus 
oregonensis) , MacPhee and Ruelle 21 screened nearly 1,900 compounds, 
including five aldehydes, for toxicity to the squawfish, steelhead 
trout (Salmo gairdnerii) , Chinook salmon (Oncorhynchus tschawytscha) , 
and coho salmon (Oncorhynchus kisutch) . Each compound was evaluated 
at only one concentration. Some of the compounds were tested with 
only some of the species. Compounds that caused death, loss of 
equilibrium, or other signs of distress were considered toxic. At 10 
ppm, anisaldehyde was toxic to all the species. At 1 ppm, polymeric 
butyraldehyde was toxic to chinook salmon, but not to the other 
species. At 10 ppm, chloral (as chloral hydrate) had no effect on any 
of the species; however, at the same concentration, mesitaldehyde was 
toxic to the squawfish, steelhead trout, and coho salmon (the chinook 
salmon was not used as a test species). At 2.5 ppm, none of the 
species was affected by salicylaldehyde. 

Applegate and co-workers 2 performed a similar study on about 
4,400 chemical compounds (including 13 aldehydes) to find one that 
would selectively affect the marine lamprey (Petromyzon marinus) . 
Other fish included in the study were the rainbow trout (Salmo 
gairdnerii) and the bluegill sunfish (Lepomis macrochirus). With some 
of the compounds, tests with the trout and bluegill were deleted. The 
test concentrations were 0.1, 1.0, and 5.0 ppm, and the maximal 
exposure time was 24 h. At 5 ppm, acrolein had no effect on any of 
the species. This result is not in agreement with those presented 
earlier. Other aldehydes that had no effect on any of the species at 
5 ppm were anisaldehyde, benzaldehyde, butyraldehyde (polymer), 
chloral, dichlorobenzaldehyde, enanthaldehyde, isobutyraldehyde, 
metacrolein, propionaldehyde, salicylaldehyde, and veratraldehyde. Of 
the aldehydes tested, only mesitaldehyde was toxic to the lamprey at 5 
ppm; it was not tested with the other fish species. 



283 

Neither of these studies showed chloral to have any effect at up 
to 10 ppm (10 mg/L) . That is surprising, because the recommended 
concentration for producing anesthesia in fish is about 2-3 mg/L, 3 
at which concentration narcosis usually occurs in less than 5 min. 



BIOCONCENTRATION 

Bioconcentration is the process by which a chemical becomes more 
concentrated in an organism than it is in the environment of the 
organism. 25 Chemicals that bioconcentrate are generally considered 
to be more hazardous than those which do not, because, at sublethal 
concentrations, they may eventually produce toxic effects as the body 
burden increases or may cause a progressive increase in the body 
burden of organisms at higher trophic levels as the compound is 
transferred through food webs or chains. 

The propensity of a chemical to bioaccumulate can be determined 
experimentally by exposing an organism to it and determining the 
concentrations of the compound in the tissues and in the exposure 
medium. The ratio of these two concentrations is called the 
bioconcentration factor (BCF) . Of the 39 aldehydes addressed in this 
chapter, acrolein is the only one for which a BCF has been 
experimentally derived. The value was 344, and it was determined with 
the bluegill sunfish (S. Petrocelli, personal communication). 

An indirect method of determining the propensity of a chemical to 
accumulate in tissues is to determine its octanol-water partition 
coefficient, which is an experimentally derived ratio of the 
concentrations of a compound in N-octanol and in water after N-octanol 
is mixed with water that contains the compound. The logarithms of the 
octanol-water partition coefficients for the 36 aldehydes are shown in 
Table 10-4. The log P values were calculated by the method of Hansch 
and Leo, 13 except that for acrolein, which was determined 
experimentally (Petrocelli, personal communication) . Hydration will 
reduce the calculated log P values of the aliphatic aldehydes by 0.38 
and will increase the values of the aromatic aldehydes by 0.39. Of 
the log P values shown, capraldehyde, caprylaldehyde, 
3 , 5-di-tert-butyl- 4-hydroxybenzaldehyde, mesitaldehyde, 
nonylaldehyde , and undecylaldehyde have values over 3.0. These may 
bioconcentrate appreciably in aquatic organisms. 



284 
TABLE 10-4 

Logarithms of Octanol-Water Partition Coefficients 
for 36 Aldehydes 3 



Aldehyde L 8 P 

Acetaldehyde -0.21 

Acrolein - 9 ^ 

Anis aldehyde 1 ' 54 

Benzaldehyde 1 - 48 

Butyr aldehyde 0.87 

Capraldehyde 4 ' 1;L 

Caproaldehyde 1.95 

Caprylaldehyde 3 * 03 

Chloral ' 51 

Cinnaraaldehyde 1<92 

Crotonaldehyde ' 55 

3 , 5-Di-tert-butyl-A-hydr oxybenzaldehyde 4.75 

Dichlorobenzaldehyde 2.00 

Dimethylbenzaldehyde 2.82 

Enanthaldehyde 2>49 

2 -Ethyl but yr aldehyde 1 73 

2-Ethylcaproaldehyde 2.81 

Formaldehyde -0.87 

Furaldehyde - 88 

Isobutyr aldehyde 0.65 

Tsopropionaldehyde 1.82 

Is ovaler aldehyde 1.28 

Mesitaldehyde 3 - 48 

Methacrolein - 33 

2-Methylpropionaldehyde 0.65 

3-Methylvaleraldehyde 1 82 

Nonylaldehyde 3.57 

Paraldehyde 1.15 

Propionaldehyde 0.33 

Salicylaldehyde I- 89 

Sorbaldehyde i- 08 

Syringaldehyde 2.15 

Undecylaldehyde 4 65 

Valeraldehyde 1.41 
Vanillin - 89 

Veratr aldehyde ! 61 



a Calculated by the method of Hansch and Leo, 13 except the value 
for acrolein, which was experimentally derived (S. Petrocelli, 
personal communication). 



285 
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3. Bell, G. R. A Guide to the Properties, Characteristics, and Uses 
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7. Butler, P. A. Effects of herbicides on estuarine fauna. 
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11. Garrett, J. T. Toxicity investigations on aquatic and marine 
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12. Gellman, I. Studies on the biochemical oxidation of sewage, 
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14. Helms, D. R. use of formalin for selective control of tadpoles in 
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15. Hermann, E. R. Toxicity index for industrial wastes. Ind. Eng. 
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286 

16. Hill, R. D. The use of acrolein, acrylaldehyde:2-propenal in the 
treatment of submerged weeds in farm ponds. Ohio Agnc. Exp. 
Stn. , 1960. 3 pp. 

17. Kemp, H. T., J. P. Abrams, and R. C. Overbeck. Water Quality 
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18. Kitchens, J. E. , R. E. Casner , G. S. Edwards, W. E. Harward III, 
and B. J. Macri. Investigation of Selected Potential 
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U.S. Environmental Protection Agency, Office of Toxic Substances, 
1976. 217 pp. 

19. Louder, D. E., and F. G. McCoy. Preliminary investigations of the 
use of aqualin for collecting fishes, pp. 240-242. In Proceedings 
of the 16th Annual Conference, Southeastern Association of Game 
and Fish Commissioners. New Orleans: Southeastern Association of 
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20. Macek, K. J., M. A. Lindberg, S. Sauter , K. S. Buxton, and P. A. 
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the Fathead Minnow (Pimephales promelas) . U.S. Environmental 
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D.C.: U.S. Government Printing Office, 1976. 68 pp. 

21. MacPhee, C., and R. Ruelle. Lethal effects of 1888 chemicals upon 
four species of fish from western North America. Univer. Idaho 
For. Wildl. Range, Exp. Stn., Bull. No. 3, 1969. 112 pp. 

22. Mattson, V. R. , J. W. Arthur, and C. T. Walbridge. Acute Toxicity 
of Selected Organic Compounds to Fathead Minnows. U.S. 
Environmental Protection Agency Report No. EPA-600/e-76-097 . 
Washington, D.C.: U.S. Government Printing Office, 1976. 12 pp. 

23. McKee, J. E. , and H. W. Wolf, Eds. Water Quality Criteria. 2nd 
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24. Middlebrooks, E. J., M. J. Caspar, R. D. Caspar, J. H. Reynolds, 
and D. B. Porcella. Effects of Temperature on the Toxicity to the 
Aquatic Biota of Waste Discharges. A Compilation of the 
Literature. PRWG Report 105-1. Washington, D.C.: U.S. Department 
of the Interior, 1973. 170 pp. 

25. National Research Council, Environmental Studies Board. 
Principles for Evaluating Chemicals in the Environment. 
Washington, D.C.: National Academy of Sciences, 1975. 454 pp. 

26. Nazareuko, J. V. Effect of formaldehyde on aquatic organisms. 
Tr. Vses. Gidrobiol. Ova. 10:170, 1960. (in Russian) 

27. Palmer, C. M. , and T. E. Maloney. Preliminary screening for 
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28. Patrick, R., J. Cairns, Jr., and A. Scheier. The relative 
sensitivity of diatoms, snails, and fish to twenty common 



287 

constituents of industrial wastes. Prog. Fish Cult. 30:137-140, 
1968. 

29. Portmann, J. E., and K. W. Wilson. Toxicity of 140 Substances to 
the Brown Shrimp and Other Marine Animals. Shellfish Information 
Leaflet No. 22. Burnham-on -Couch, Essex, England: Ministry of 
Agriculture, Fish, and Food; Fisheries Laboratory, 1971. 12 pp. 

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Fish and Wildlife Service Report FWS/LR-74/09. Springfield, 
Virginia: National Technical Information Service, Publication No. 
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31. Turnbull, H. , J. G. DeMann, and R. F. Weston. Toxicity of various 
refinery materials to fresh water fish. Ind. Eng. Chem. 
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Environmental Protection Agency Report No. EPA 440/5-80-016. 
Washington, D.C.: U.S. Government Printing Office, 1980. 100 pp. 

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Wildlife. Fish Disease Manual. Region 3. 1971. 183 pp. 
Available from National Fisheries Center, Kearneysville, W. Va. 

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35. Wilber, C. G. The Biological Aspects of Water Pollution. 
Springfield, Illinois: Charles C Thomas, 1969. 296 pp. 



APPENDIX 
Properties, Uses, and Synonyms of Selected Aldehydes 

KEY TO TABLES A-l AND A-2 
Aldehyde Entry in Tables A-l and A-2 



p-Ac e t al de hy de 

Acetaldol 

Acetic aldehyde 

Acetylformaldehyde 

Acetylformyl 

Acrolein 

Acrylaldehyde 

Acrylic aldehyde 

AgriStrep 

Aldehyde B 

Aldehyde C-7 

Aldehyde C-8 

Aldehyde C-10 

Aldehyde C-12 

Aldehyde M.N.A. 

Aldesan 

Aldol 

Allyl aldehyde 

Amylcinnamaldehyde 

a-Amylcinnamaldehyde 

a-Arayl-3-phenylacrolein 

Anhydrous chloral 

m-Anisaldehyde 

-Ani sal de hy de 

p-Anisaldehyde 

2-Anisaldehyde 

4-Ani saldehyde 

-Anisic aldehyde 

^-Anisic aldehyde 

Antifoam-LF 

Aqualin 

Artificial almond oil 

Aub epine 

Benzaldehyde-2 , 4-disulfonic 

acid 

Benzaldehyde FFC 
Benzaldehyde-j>-sulfonic acid 

sodium salt 
Benzeneacetaldehyde 
Benzenecarb onal 
Benzenecarb oxaldehyde 
-Benzenedicarboxaldehyde 
Benzoic aldehyde 



ACETALDEHYDE, Par aldehyde 

BUTANAL, 3-Hydroxy- 

ACETALDEHYDE 

PROPANAL, 2-Oxo- 

PROPANAL, 2-Oxo- 

2 -PRO PENAL 

2-PROPENAL 

2 -PRO PENAL 

STREPTOMYCIN sulfate 

PROPANAL, a-Methyl-4-(l-methyl- 

ethyl)benzene- 
n-HEPTANAL 
OCTANAL 
DECANAL 
DECANAL, Do- 
UNDECANAL, 2-Methyl- 
1 , 5-PENTANED1AL 
BUTANAL, 3-Hydroxy- 
2-PROPENAL 

HEPTANAL, 2-(Phenylmethylene)- 
HEPTANAL, 2-(Phenylmethylene)- 
HEPTANAL, 2-(Phenylmethylene)- 
ACETALDEHYDE, Trichloro- 
BENZALDEHYDE, 3-Methoxy- 
BENZALDEHYDE, 2-Methoxy- 
BENZALDEHYDE, 4-Methoxy- 
BENZALDEHYDE, 2-Methoxy- 
BENZALDEHYDE, 4-Methoxy- 
BENZALDEHYDE, 2-Methoxy- 
BENZALDEHYDE, 4-Methoxy- 
OCTANAL 
2-PROPENAL 
BENZALDEHYDE 
BENZALDEHYDE, 4-Methoxy- 
BENZ ALDEHYDE , 4-F ormy 1-1 , 3- 

benzenedisulfonic acid 
BENZALDEHYDE 
BENZALDEHYDE, 2-Formylbenzene- 

sulfonic acid sodium salt 
ACETALDEHYDE, Benzene 
BENZALDEHYDE 
BENZALDEHYDE 

1 , 4-BENZENEDICARBOXALDEHYDE 
BENZALDEHYDE 



289 



290 



Be nzylacet aldehyde 

Benzylideneacetaldehyde 

Biformal 

Biformyl 

Bourbonal 

Butal 

But aldehyde 

n- But anal 

Butanaldehyde 

trans-2-Butenal 

Butyl aldehyde 

jQ-Butyl aldehyde 

p-tert-Butylbenzaldehyde 

4-tert-Butylbenzaldehyde 

_t-Butylcarboxaldehyde 
4-tert-Butylcyclohexane- 

carboxaldehyde 
_t-Butylfonnaldehyde 
4-tert-Butylhexahydro- 

benz aldehyde 
p-tert-Butyl-g-methylhydr o- 

cinnamaldehyde 
Butyral 
Butyraldehyde 
n-Butyr aldehyde 
Butyric aldehyde 
Butyrylaldehyde 
BVF 



PROP ANAL, Benzene- 

2-PRO PENAL, 3-Phenyl- 

ETHANEDIAL 

ETHANEDIAL 

BENZALDEHYJJE, 3-Ethoxy-^f- 

hydroxy- 
BUTANAL 
BUTANAL 
BUT ANAL 
BUTANAL 
2-BUTENAL 
BUTANAL 
BUTANAL 
BE NZ ALDEHYDE, 

ethyl)- 
BENZ ALDEHYDE, 

ethyl)- 

PROPANAL, 2,2-Dimethyl- 
CYCLUHJiXAlvlJiCARBOXALDEHYDE s 

(1,1-Dinethylethyl)- 
PROPANAL, 2,2-Dimethyl- 
CYCLOHEXANECARBOXALDEHYDE . 

(1,1-Dimethylethyl)- 
PROPANAL, 4-(l,l-Dimethylethyl)' 

a~methylbenzene- 
BUTANAL 
BUTANAL 
BUTANAL 
BUTANAL 
BUTANAL 
FORMALDEHYDE 



4-(l,l-Dimethyl- 
4-(l,l-Dimethyl- 

4- 
4- 



Capraldehyde 

Capric aldehyde 

Caprinaldehyde 

Caprinic aldehyde 

Caproaldehyde 

n-Caproaldehyde 

Caproic aldehyde 

Capronaldehyde 

Caprylaldehyde 

ii-Caprylaldehyde 

Caprylic aldehyde 

Carbomethene 

Cassia aldehyde 

Chloral 

-Chlorobenzaldehyde 

_p_-Chlorobenzaldehyde 



DECANAL 

DECANAL 

DECANAL 

DECANAL 

HEXANAL 

HEXANAL 

HEXANAL 

HEXANAL 

OCTANAL 

OCTANAL 

OCTANAL 

ETHENONE 

2-PROPENAL, 3~Phenyl- 

ACETALDEHYDE , Trichloro- 

BENZALDEHYDE, 2-Chloro- 

BENZALDEHYDE, 4-Chloro- 



291 



4-((2-Chloroethyl)ethylamino)- 

jD-tolualdehyde 
j>-((2-Chloroethyl)methylamino)- 

benzaldehyde 
Cinnamal 
Cinnamaldehyde 
Cinnamic aldehyde 
Cinnamyl aldehyde 
Citral 

Citronellal hydrate 
Citronelloxyacetaldehyde 

Coniferaldehyde 
-Coniferaldehyde 
Coniferyl aldehyde 

Crategine 
Crotonal 
Crotonaldehyde 
Crotonic aldehyde 
Crotylaldehyde 
Cumaldehyde 
Cumene aldehyde 
Cumic aldehyde 
Cuminal 

-Cuminal dehy de 
Cuminic aldehyde 
Cuminyl aldehyde 
Cyclalia 
Cyclamal 

Cyclamen aldehyde 

3-Cyclohexen-l-aldehyde 
Cyclohexene-4-carboxaldehyde 
Cyclosia 
p-Cymene-7-carboxaldehyde 

Decaldehyde 

n-Decaldehyde 

n-De canal 

Decanal de hyde 

Decyl aldehyde 

n-Decyl aldehyde 

Decylic aldehyde 

-2-Deoxy-2-(methylamino)-a-l-gluco- 
pyranosyl-(l-4)-N,N/-bis(amino- 
iminome thyl ) D-s tr ep tamine 

Diethylacetaldehyde 



BENZALDEHYDE, 4-( (2-Chloro- 

ethyl)ethylamino)-2-met:hyl- 
BENZALDEHYDE, 4( (2-Chlo roe thyl) - 

methylamino)- 
2-PROPENAL, 3-Phenyl- 
2-PROPENAL, 3-Phenyl- 
2-PROPENAL, 3-Phenyl- 
2-PROPENAL, 3-Phenyl- 
2,6-OCTADIENAL, 3,7-Dimethyl- 
OCTANAL, 7-Hydroxy-3,7-dimethyl- 
ACETALDEHYDE, 3, 7-Dimethyl-6- 

octenyloxy- 
2-PROPENAL, 3-(4-Hydroxy-3- 

methoxyphenyl)- 
2-PROPENAL, 3-(4-Hydroxy-3- 

me t ho xy pheny 1 ) - 
2-PROPENAL, 3-(4-Hydroxy-3- 

methoxyphenyl)- 
BENZ ALDEHYDE, 4-Methoxy- 
2-BUTENAL 
2-BUTENAL 
2-BUTENAL 
2-BUTENAL 

BEUZALUEUYDE, 4-( 1-Methylethyl)- 
ACETALDEHYDE, a-Methylbenzene- 
BENZALDEilYDE, 4- (1-Me thyl ethyl )- 
BENZALDEHYDE, 4-(.l-Methyiethyl)- 
BENZALDEHYDE, 4-(l-Methylethyl)- 
BENZALDEHYDE, 4- (1-Me thy le thyl )- 
BENZALDEHYDE, 4-(l-Methylethyl)- 
OCTANAL, 7-Hydroxy-3 , 7-dimethyl- 
PROPANAL , o-Methyl-4-( 1-methyl- 

ethyl)benzene- 
PROPANAL, a-Methyl-4-(l-methyl- 

ethyl)benzene- 

3-CYCLOHEXENE-l-CARBOXALDEHYDE 
3- C YCLOHEXE NE-1 -C ARBO XALDEHY DE 
OCTANAL, 7-Hydroxy-3,7-dimethyl- 
ACETALDEHYDE , 4-(l-Methylethyl)- 

benzene- 
DE CANAL 
DECANAL 
DECANAL 
DECANAL 
DECANAL 
DECANAL 
DECANAL 
STREPTOMYCIN 



BUT ANAL, 2-Ethyl- 



292 



j>-(Diethylamino)benzaldehyde 

Diformyl 

1 , 4-DIformylbenzene 

Dihyd rocinnamaldehyde 

( 1 , 3-Dihydro-l , 3 , 3-triraethyl-2H- 
indol-2-ylidene)-acetaldehyde 

3 , 4-Dihydroxybenzaldehyde 
methylene ketal 

3, 4-Dimethoxybenzenecarbonal 

3,5-Dimethoxy-4-hydroxybenzaldehyde 

3 , 5-Dimethoxy-4-hydroxybenzene 

carbonal 

Dimethyl acet aldehyde 
a , 4-Dimethylbenzeneacetaldehyde 

3 , 4 -Dime thylenedioxybenzaldehyde 

2 , 6-Dimethyl-5-hepten-l-al 
3 , 7-Dimethyl-7-hydroxyoctanal 
3 , 7-Dimethyl-6-octenal 
3 , 7-Dimethyl-6-octenyl-oxy- 

acetaldehyde 
6 , 10-Dimethyl-3-oxa-9-undecanal 

a, a-Dimethylpropanal 
a, a-Dimethylpropionaldehyde 
2 , 2-Dimethylpropionaldehyde 
2 , 4 -Disulf obenz aldehyde 

^i-Dode canal 
1 -Do dec anal 
Dodecanaldehyde 
Dodecyl aldehyde 
ja-Dodecyl aldehyde 
Dodecylic aldehyde 



BENZ ALDEHYDE, 4-(Diethylaiaino)- 

ETHANEDIAL 

1 , 4-BENZENEDICARBOXALDEHYDE 

PROPANAL, Benzene- 

ACETALDEHYDE, 1 , 3, 3-Trimethyl-A- 

(2,ot)-indoline- 
1 , 3-BENZODTOXOLE-5-CARBOX- 

ALDEHYDE 

BENZALDEHYDE, 3,4-Dimethoxy- 
BENZALDEHYDE, 4-Hydroxy-3,5- 

dimethoxy- 
BENZALDEHYDE, 4-Hydroxy-3,5- 

dimethoxy- 
PROPANAL, 2 -Methyl - 
ACETALDEHYDE, a ,4-Dimethyl- 

benzene- 
1 ,3-BENZODIOXOLE-5-CARBOX- 

ALDEHYDE 

HEPTENAL, 2,6-Dimethyl-5- 
OCTANAL, 7-Hydroxy-3,7-diraethyl- 
CITRONELLAL (d_ isomer) 
ACETALDEHYDE, 3, 7 -Dimethyl -6- 

octenyl-oxy- 
ACETALDEHYDE, 3,7-Dimethyl-6- 

octenyl-oxy- 
PROPANAL, 2,2-Dimethyl- 
PROPANAL, 2,2-Dimethyl- 
PROPANAL, 2,2-Diraethyl- 
BENZALDEHYDE , 4-Formyl-l , 3- 

benzenedisulfonic acid 

DECANAL, DO- 
DECANAL, Do- 
DECMAL, DO- 
DECANAL, DO- 
DECANAL, DO- 
DECANAL, Do- 



Enanthal 

E nan thai dehyde 

Enanthic aldehyde 

Enanthole 

Epihydrinaldehyde 

2 , 3-Epoxypropanal 

2 , 3-Epoxypropionaldehyde 

Ethanal 

Ethanedione 

1 , 2-Ethanedione 



n-HEPTANAL 

n-HEPTANAL 

n-HEPTANAL 

n-HEPTANAL 

OXIRANECARBOXALDEHYDE 

OXIRANECARBOXALDE HYDE 

OXIRANECARBOXALDEHYDE 

ACETALDEHYDE 

ETHANEDIAL 

ETHANEDIAL 



293 



Ethavan 
Ethovan 
4-E thoxy-m-ani s aide hyde 

Ethoxybenzaldehyde 
jr-Ethoxybenzaldehyde 
3~Ethoxy-a-ketobutyr aldehyde 
Ethyl aldehyde 
a-Ethylbutyr aldehyde 
2-Ethylbutyr aldehyde 
2-Ethylbutyric aldehyde 
Ethylprotal 

Ethylvanillin 



BEUZ ALDEHYDE, 3-bthoxy-4- 

hydroxy- 
BENZALDEHYDh, J-Ethoxy-4- 

hydroxy- 
BENZALDEHYDE, 4-Ethoxy-3- 

methoxy- 

BENZALDEHYDE, 4-Ethoxy- 
BENZALDEHYDE, 4-Ethoxy- 
BUTANAL, 3-Ethoxy-2-oxo- 
ACETALDEHYDE 
BUT ANAL, 2-Ethyl- 
BUTANAL, 2-Ethyl- 
BUTANAL, 2-Ethyl 
BENZALDEHYDE, 3-Ethoxy-4- 

hydroxy- 
BENZALDEHYDE, 3-Ethoxy-4- 

hydroxy- 



Fannofonn 
Ferul aldehyde 

Fisher's aldehyde 

Fixol 

Flomine 

Flo-Mor 

Formaldehyde solution 

Formaldehyde trimer 

Formalin 

Formalith 

Formic aldehyde 

Formol 

-Formylanisole 

-Formylbenzaldehyde 

4-Eormylbenzaldehyde 

a-Formylbenzene acetic acid 

4 Formyl-m-benzenedisulfonic acid 
o_-Formylbenzenesulfonic acid 

o_-Formylbenzenesulfonic acid 

sodiiim salt 
5-Formyl-l ,3-benzodioxole 

2 Formyl butane 

1 Formyl-3-cyclohexene 

4 -Fo rmyl eye lohexene 

-Formyl-N;,N-diethylaniline 



FORMALDEHYDE 

2-PROPENAL, 3-(4-Hydroxy-3- 

me thoxyphenyl )- 
ACETALDEHYDE , 1,3,3-Tnraethyl-A- 

(2,a)-indoline- 

OCTANAL, 7-Hydroxy-3,7-dimethyl- 
HEPTANAL, 2-(Phenylraethylene)- 
FORMALDEHYDE , Para- 
FORMALDEHYDE 

FORMALDEHYDE, 1 ,3,5-Trioxane 
FORMALDEHYDE 
FORMALDEHYDE 
FORMALDEHYDE 
FORMALDEHYDE 
BENZALDEHYDE, 4-Methoxy- 
BE NZENED ICARBOXALDEHYDE , 1,4- 
1 ,4-BENZENEDICARBOXALDEHYDE 
ACETALDEHYDE , a-Formylbenzene 

acetic acid 
BENZALDEHYDE, 4-Formyl-l,3- 

benzenedisulfonic acid 
BENZALDEHYDE, 2-Formylbenzene- 

sulfonic acid 
BENZALDEHYDE, 2-Formylbenzene- 

sulfonic acid sodium salt 
1 , 3-BENZODIOXOLE-5-CARBOX- 

ALDEHYDE 

BUTANAL (dl), 2-Methyl- 
3-CYCLOHEXE NE-1 -C ARBOXALDEHYDE 
3-CYCLOHEXENE-l-CARBOXALDEHYDE 
BENZALDEHYDE, 4-(Diethylamino)- 



294 



2-Formylf uran 
5-Formylguaiacol 

6 -Fo rraylguaiacol 

a-Formyliso butyl benzene 
4-Formyl-2-methoxyphenol 

6-Formyl-2-methoxyphenol 

2-(Formylmethylene)-l,3,J-trimethyl- 

indoline 
3-Formyl-2-methylindole 

1 -Fo rmy 1-2-napht ho 1 

2-Fo nny Ipen t ane 
3-Fo rmylpentane 
jn-Fo rraylphenol 
cr-Formyl phenol 
jo-Formylphenol 
2-Formylphenol 
3-Fonnylphenol 
a-Formylphenylacetic acid 

2-Formylpyridine 

-Fo rrayl t o lue ne 

2 -Formyl toluene 

3-Formyl toluene 

Fural 

Fur aldehyde 

a -Fur aldehyde 

2-Fur aldehyde 

Fur ale 

2-Fur anal dehyde 

Furancarbonal 

2-Fur ancarbonal 

Furfural 

2-Furfural 

Furfuraldehyde 

2-Fur fur aldehyde 

Furfurole 

Furfurylaldehyde 

Furole 

a-Furole 

2-Furylaldehyde 

Fyde 



BE NZ ALDEHYDE 
BENZALDEHYDE 
BENZ ALDEHYDE 
BENZALDEHYDE 



2-FURANCARBOXCALDEHYDE 
BENZALDEHYDE, 3-Hydroxy-4- 

methoxy- 
BENZ ALDEHYDE, 2-Hydroxy-3- 

methoxy- 

BUTANAL, 3-Methyl-2-phenyl- 
BENZ ALDEHYDE, 4-Hydroxy-3- 

methoxy- 
BENZALDEHYDE, 2-riydroxy-3- 

methoxy- 
ACETALDEHYDE, i,3,3-Trimethyl-A- 

(2,a)indoline- 
INDOLE-3-CARBOXALDEHYUE, 2- 

Methyl-lH- 
2-Hyd r oxy- 1 -NAPHTHALENECARBOX- 

AL DEHYDE 

PENT ANAL, 2-Methyl- 
BUTANAL, 2-Ethyl- 
BENZALDEHYDE, 3-Hydroxy- 
2-Hydroxy- 
4 -Hydro xy- 
2-Hydroxy- 
3-Hydroxy- 
ACETALDEHYDE, a -Formyl benzene 

acetic acid 

2-PYRIDINECARBOXALDEHYDE 
BENZALDEHYDE, 4-Methyl- 
BENZALDEHYDE, 2-Methyl- 
BENZALDEHYDE, 3-Methyl- 
2-FURANCARBOXALDEHYDE 
2-FURANC ARBOXAL DE HYDE 
2-FURANCARB OXALDEHYDE 
2-F URANC ARBOXALDE HYDE 
2-FURANCARBOXALDEHYDE 
2-FURANCARBOXALDEHYDE 
2 -FURANC ARE OXALDE HYDE 
2-FURANCARBOXALDEHYDE 
2 -FURANCARBOXALDEHYDE 
2-FURANCARBOXALDEHYDE 
2-FURANCARBOXALDEHYDE 
2-FURANCARBOXALDEHYDE 
2-FURANCARBOXALDEHYDE 
2-FURANCARBOXALDE HYDE 
2-FURANCARBOXALDEHYDE 
2-FURANCARBOXALDEHYDE 
2-FURANCARBOXALDEHYDE 
FORMALDEHYDE 



Gallaldehyde 3,5-dimethyl ether 



BENZALDEHYDE, 4-Hydroxy-3,5- 
dimethoxy- 



295 



Geliotropin 

Geranial 

Ge rani aldehyde 

Glutaral 

Glut ar aldehyde 

Glutardialdehyde 

Glutaric dialdehyde 

Glycidal 

Glyc id aldehyde 

Glyoxal 

Glyoxal aldehyde 

Glyoxylaldehyde 



1 , 3-BENZODIOXOLE-5- 
CARBOXALDEHYDE 

2,6-OCTADIENAL, 3, 7 -Dime thy 1- 
2,6-OCTADIENAL, 3,7-Dimethyl- 
1,5 -PENT ANEDIAL 
1,5-PENTANEDIAL 
1,5-PENTANEDIAL 
1,5-PENTANEDIAL 
OXIRANECARBOXALDEHYDE 
OXI RANECARBOXALDE HYDE 
ETHANE DIAL 
ETHANEDIAL 
ETHANE DIAL 



Heliotropin 
Heliotr opine 

Hende canal 

Hendecanaldehyde 

Heptaldehyde 

n-Hept aldehyde 

Heptanal 

Heptanaldehyde 

_n-Heptylaldehyde 

2,4-Hexadien-l-al 

Hexaldehyde 

n-Hexanal 

(E)-2-Hexenal 

trans-Hex-2-enal 

2- 1 r an s -Hexen al 

t :r ans- 2-Hexenal 

trans-2-Hexen-l-al 

a-n-Hexyl cinnam al dehyd e 

Hexyl cinnatnic aldehyde 

Hexylenic aldehyde 

a-n-Hexyl- 3-phenylacrolein 

Hospex 

Hyacinthal 

Hyacinthin 

Hydratropa aldehyde 

Hydratropaldehyde 

Hydratropic aldehyde 

Hydrocinnamaldehyde 

Hydrocinnamic aldehyde 

2-Hydroxy-m-anisaldehyde 

3 -Hydr oxy--anis aldehyde 



1 , 3-BENZODIOXOLE-5-CARBOX- 

ALDEHYDE 
1 , 3-BENZODIOXDLE-5-CARBOX- 

ALDEHYDE 
UNDE CANAL 
UNDE CANAL 
_n-HEPTANAL 
n-HEPTANAL 
ri-HEPTANAL 
n-HEPTANAL 
n-HEPTANAL 
2,4-HEXADIENAL 
HEXANAL 
HEXANAL 
HEXENAL, 2- 
HEXENAL, 2- 
HEXENAL, 2- 
HEXENAL, 2- 
HEXENAL, 2- 

OCTANAL, 2-(Phenylmethylene)- 
OCTANAL, 2-(Phenylmethylene)- 
HEXENAL 

OCTANAL, 2-(Phenylmethylene)- 
1,5-PENTANEDIAL 
ACETALDEHYDE, ot-Methylbenzene- 
ACETALDEHYDE, Benzene 
ACETALDEHYDE, ct-Methylbenzene- 
ACKTALDEHYDE, ot-Methylbenzene- 
ACETALDEHYDE, ct-Methylbenzene- 
PROPANAL, Benzene- 
PROPANAL, Benzene- 
BENZ ALDEHYDE, 2-Hydroxy-3- 

methoxy- 
BENZ ALDEHYDE, 3-Hydroxy-4- 

methoxy- 



296 



4-Hydroxy-m-anisaldehyde 

in-Hydroxyben zaldehyde 

o-Hydroxybenzaldehyde 

jD-Hydroxybenzaldehyde 

g-Hydroxybutanal 

Hydroxycitronellal 

7-Hydroxycitronellal 

4-Hydroxy-3,5-diraethoxy- 

cinnamaldehyde 
4-Hydr oxy-3-e thoxyben zaldehyde 

jD-Hydroxy-m-methoxybenzaldehyde 
4 -Hyd r oxy-3-me thoxycinnamal deh yde 

4-(4-Hydroxy-4-methylpentyl)-A - 
tetrahydrobenz aldehyde 

2-Hydroxynaphthaldehyde 
2 -Hyd roxy-a-naphth aldehyde 
2-Hydroxy-l-naphthaldehyde 
2 -Hydr oxy- 1-naphthyl aldehyde 



BE1JZ ALDEHYDE, 4-Hydroxy-3- 

methoxy- 

BENZALDEHYDE, 3-Hydroxy- 
BENZALDEHYDE, 2-Hydroxy- 
BENZ ALDEHYDE, 4-Hydroxy- 
bUTANAL, 3-Hydroxy- 
OCTANAL, 7-Hydroxy-3,7-diraethyl- 
OCTANAL, 7-Hydroxy-3,7-dimethyl- 
2-PRO PENAL, 3-(4-Hydroxy-3,5- 

diraethoxyphenyl)- 
BENZALDEHYDE, 3-Ethoxy-4- 

hydroxy- 
BENZALDEHYDE, 4-Hydroxy-3- 

methoxy- 
2 -PRO PENAL, 3-(4-Hydroxy-3- 

methoxyphenyl)- 
3-CYCLOHEXENE-l-CARBOXALDEHYDE , 

4-(4-Hydroxy-4-methyl- 

pentyl)- 
NAPHTHALENECARBOXALDEHYDE, 2- 

Hydroxy-1- 
NAPHTHALENECARBOXALDEHYDE, 2- 

Hydroxy-1- 
NAPHTHALENECARBOXALDEHYDE, 2- 

Hydroxy-1- 
NAPHTHALENECARBOXALDEHYDE, 2- 

Hydroxy-1- 



Isobutanal 
Isobutenal 
Isobutyr aldehyde 
Isodihydrolavandulyl aldehyde 

Isopentanal 

Isophthal aldehyde 

Isopropyl aldehyde 

jp_-Isopropylbenzaldehyde 

4-Isopropylbenzaldehyde 

Isopropyl formaldehyde 

2-Isopropylidene-5-tnethyl-4-hexenal 

j>-Isopropyl-a-ciethylhydro- 

cinnam aldehyde 
(^-Isopropylphenyl)acetaldehyde 

3-(4-Isopropylphenyl)-2-methyl- 

propanal 
j^-Isopropylphenyl-a-methyl- 

propyl aldehyde 
Isovaleral 



PROPANAL, 2-Methyl- 
2-PROPENAL, 2-Methyl- 
PROPANAL, 2-Methyl- 
HEXENAL, 5-Methyl-2-(l-methyl- 

ethylidene)4- 
BUTANAL, 3-Methyl- 
BENZENEDICARBOXALDEHYDE, 1,3- 
PROPANAL, 2-Methyl- 
BENZ ALDEHYDE, 4- (1 -Methyl ethyl ;- 
BENZALDEHYDE, 4-(l-Methylethyl> 
PROPANAL, 2-Methyl- 
HEXENAL, 5-tfethyl-2-(l-methyl- 

ethylidene)4- 
PROPA14AL, a-Methyl-4-(l- 

me thyl ethyl) benzene- 
ACETALDEHYDE, 4-(l-Methylethyl)- 

benzene- 
PROPANAL, a-Methyl-4- 

( 1 -me thyl ethyl )benze ne- 
PROPANAL, a-Methyl-4- 

(l-methylethyl)benzene- 
BUTAHAL, 3-Methyl- 



297 



Isoval e raldehyde 
Isovaleric aldehyde 
Isovanillin 

Ivalon 



BUTANAL, 3-Methyl- 
BUTANAL, 3-Methyl- 
BENZ ALDEHYDE, 3-Hydroxy-4- 

raethoxy- 
FORMALDEHYDE 



Jasminaldehyde 



HEPTANAL, 2-(Phenylmethylene)- 



Ketene 

Kethoxal 

a-Ketopropionaldehyde 

2-Ketoproplonaldehyde 



ETHENONE 

BUTANAL, 3-Ethoxy-2-oxo- 
PROPANAL, 2-Oxo- 
PROPANAL, 2-Oxo- 



Lauraldehyde 

n-Laur aldehyde 

Laurie aldehyde 

Laurine 

Leaf aldehyde 

Lilial 

Lilyal 

Lilyl 
Lioxin 

Lyral 
Lysoform 



DECANAL, DO- 
DECANAL, DO- 
DECANAL 

OCTANAL 



Do- 

7-Hyd roxy-3 , 7-dime thyl- 



HEXENAL, 2- 

PROPANAL, 4-( 1 , 1-Diinethylethyl)- 

a-methylbenzene- 
PROPANAL, 4-(l,l-Dimethylethyl)- 

a-methylbenzene- 
OCTANAL, 7-Hydroxy-3,7-dimethyl- 
BENZ ALDEHYDE, 4-Hydroxy-3- 

methoxy- 

3-CYCLOHEXEHE-l-CARBOXALDEHYDE , 
4-( 4-Hydroxy-4-methylpentyl)- 
FORMALDEHYDE 



Malonaldehyde 

Malondi aldehyde 

Malonic di aldehyde 

Malonyldialdehyde 

Metaformaldehyde 

Methacrolein 

2-Methacrolein 

Methacrylaldehyde 

Methacrylic aldehyde 

Met ban al 

Methional 

ni-Methoxybenzaldehyde 

-Methoxybenzaldehyde 

^-Methoxybenzaldehyde 



PROPANEDTAL 

PROPANEDIAL 

PROPANEDIAL 

PROPANEDIAL 

FORMALDEHYDE , 1,3, 5-Tr ioxane 

2 -PRO PENAL, 2-Methyl- 

2-PROPENAL, 2-Methyl- 

2- PRO PENAL, 2-Methyl- 

2-PROPENAL, 2-Methyl- 

FORMALDEHYDE 

PROP ANAL, 3- (Methyl thio) - 

BE NZ ALDEHYDE, 3-Methoxy- 

BENZALDEHYDE , 2-Methoxy- 

BENZALDEHYDE, 4-Methoxy- 



298 



2-Methoxybenzenecarboxaldehyde 
jD-Me t boxy c innamal deh yd e 
2-Methoxycinnamaldehyde 
jD-Methoxycinnamic aldehyde 
2-Methoxy-4-formylphenol 

3 -Me t hoxy-2-hydr oxybenz aldehyde 
3-Methoxy-4-hydroxybenzaldehyde 
3-Methoxysalicylaldehyde 

Me thylacet aldehyde 
a-Methylacrolein 
3-Methylacrolein 
2-Methylacrolein 
Me thy lac r yl aldehyde 
Methyl aldehyde 
in-Methylbenzaldehyde 
o>-Methylbenzaldehyde 
jv-Methylbenz aldehyde 
a-Me t hy 1 but anal 
3-Methyl but anal 
2 -Me thylbut anal-4 
E-2-Methyl-2-butenal 
trans-2-Methyl-2-butenal 
g-Methyl-p-(tert-butyl)- 
hydrocinammaldehyde 
a-Methylbutyr aldehyde 
2-Methylbutyr aldehyde 
3-Methyl but yr aldehyde 
a-Me thyl butyric aldehyde 
2-Methylbutyric aldehyde 
a-Methylcinnamaldehyde 
a-Methylcinnamic aldehyde 
2-Methylcrotonaldehyde 
3,4-(Methylenedioxy)benzaldehyde 

Methylene oxide 
Methylethylacetaldehyde 
Methylf o rmaldehyde 
2-Methyl-3-formylindole 

Methylglyoxal 

j>-Me thy Ihydratr opal dehyde 

j>-Methylhydratropicaldehyde 
2-Methylindole-3-carboxaldehyde 

l-Methyl-4-isohexylcyclohexane-l- 
carboxaldehyde 



BE NZ ALDEHYDE, 2-Methoxy- 
2 -PRO PENAL, 3-(2-Methoxyphenyl)- 
2-PROPENAL, 3-(2-Methoxyphenyl)- 
2-PROPEMAL, 3-(2-Methoxyphenyl)- 
BENZALDEHYDE, 4-Hydroxy-3- 

methoxy- 
BENZALDEHYDE, 2-hydroxy-3- 

methoxy- 
BENZALDEHYDE, 4-Hydroxy-3- 

inethoxy- 
BENZ ALDEHYDE, 2-Hydroxy-3- 

methoxy- 
PROPANAL 

2-PROPENAL, 2-Methyl- 
2-BUTENAL 

2-PROPENAL, 2-Methyl- 
2-PROPENAL, 2-Methyl- 
FORMALDEHYDE 
BENZALDEHYDE, 3-Methyl- 
BENZALDEHYDE, 2-Methyl- 
BENZALDEHYDE , 4-Methyl- 
BUTANAL (djL), 2-Methyl- 
BUTANAL, 3-Methyl- 
BUTANAL, 3 -Me thyl - 
2-BUTENAL (E), 2-Methyl- 
2-BUTENAL (E), 2-Methyl- 
PROPANAL, 4-(l,l-Dimethylethyl)- 

a-methylbenzene- 
BUTANAL (dJ), 2-Methyl- 
BUTANAL (dl), 2-Methyl- 
BUTANAL, 3 -Me thy 1- 
BUTANAL (dl), 2-Methyl- 
BUTANAL (dl), 2-Methyl- 
2-PROPENAL, 2-Methyl-3-phenyl- 
2-PRO PENAL, 2-Methyl-3-phenyl- 
2-BUTENAL (E), 2-Methyl- 
1 ,3-BENZODIOXOLE-5-CARBOX- 

ALDEHYDE 
FORMALDEHYDE 
BUTANAL (dl), 2-Methyl- 
ACETALDEHYDE 
INDOLE-3-CARBOXALDEHYDE, 2- 

Methyl-lH- 
PROPANAL, 2-Oxo- 
ACETALDEHYDE , a , 4-Dimethyl- 

benzene- 
ACETALDEHYDE, a , 4-Dimethyl- 

benzene- 
INDOLE-3-CARBOXALDEHYDE, 2- 

Methyl-lH- 
BENZALDEHYDE, l-Methyl-4-iso- 

hexylhexahydro- 



299 



a-Methyl-p-isopropylhydro- 

cinnamaldehyde 
2-Methyl-3-(-isopropylphenyi; 

propionaldehyde 

B-(Methylmercapto)propionaldehyde 
3-(Methyliuercap to) propionaldehyde 
l-Methyl-4(4-methylpentyl)cyclo- 

hexane- 1-carboxaldehyde 
Methylnonylacetaldehyde 
Methyl-n-nonyl ace t aldehyde 
Methyl nonyl acetic aldehyde 
a-Methylpentanal 
jv-Methylphenylacetaldehyde 
( 4-Methylphenyl)acetaldehyde 
2-Metnyl-3-phenylacrolein 
2-Methyl-3-phenylacrylaldehyde 
2-(j)-Me thy Iphenyl) propionaldehyde 

2-Methylpropenal 

a-Methylpropionaldehyde 

2-Methylpropionaldehyde 

3-(Methylthio)propionaldehyde 

3-Methylthiopropionaldehyde 

ot-Methyl-a-toluic aldehyde 

2-Methyl-l-undecanal 

2-Methylvaleraldehyde 

Methylvanillin 

Morbicid 

Muguet synthetic 

Muguettine 

Myristaldehyde 

Myristylaldehyde 



PROPANAL , a-Methyl-4-( 1 -methyl- 
ethyl Jbenzene- 
PROPAWAL, a-Methyl-4-(l-methyl- 

ethyl)benzene- 
PROPANAL, 3-(Methylthio)- 
PROPANAL, 3-(Methylthio)- 
BENZALDEHYDE, l-Methyl-4-iso- 

hexylhexahydro- 
UNDECANAL, 2-Methyl- 
UNDECANAL, 2-Methyl- 
UNDECANAL, 2-Methyl- 
PENTANAL, 2-Methyl- 
ACETALDEHYDE , 4-Methylbenzene- 
ACETALDEHYDE, 4-Methylbenzene- 
2-PROPENAL, 2-Methyl-3-phenyl- 
2-PROPENAL, 2-Methyl-3-phenyl- 
ACETALUEHYDE, a ,4-Dimethyl- 

benzene- 

2-PROPENAL, 2-Methyl 
PROPANAL, 2-Methyl- 
PROPANAL, 2-Methyl- 
PROPANAL, 3-(Methylthio)- 
PROPANAL, 3-(Methylthio)- 
ACETALDEHYDE, a-Methylbenzene- 
UNDECANAL, 2-Methyl- 
PENTANAL, 2-Methyl- 
BENZALDEHYDE, 3,4-Dimethoxy- 
FORMALDEHYDE 

OCTANAL, 7-Hydroxy-3,7-dimethyl- 
OCTANAL , 7-Hydroxy-3 , 7-dime thyl- 
DECANAL, Tetra- 
DE CANAL, Tetra- 



3-Naphthol-l-aldehyde 
2-Naphthol-l-carboxaldehyde 

Neopentanal 
^-Nlcotinaldehyde 
_m-Nitrobenzaldehyde 
Nonaldehyde 
n-Nonaldehyde 
Nonanoic aldehyde 
n-Nonylaldehyde 
Nonylic aldehyde 
NSC 8819 



2-iiydroxy-l-NAPHTHALENECARBOX- 

ALDEHYDE 
2-Hydroxy- 1-NAPHTHALENECARBOX- 

ALDEHYDE 

PROPANAL, 2,2-Diraethyl- 
2-P YR1D INECARBOXALDEHYDE 
BENZ ALDEHYDE, 3-Nitro- 
NONANAL 
NONANAL 
NONAI'JAL 
NONANAL 
NONANAL 
2-PROPENAL 



300 



Obepin 

Octaldehyde 

n-Oct aldehyde 

n-Octanal 

Octanaldehyde 

Octanoic aldehyde 

jn-Octylal 

Octylaldehyde 

Oenanthal 

Oenanthaldehyde 

Oenanthic aldehyde 

Oenanthol 

Oenanthole 

Oxal 

Oxalaldehyde 

Ox orae thane 

jy-Oxybenzaldehyde 

Oxymethylene 



BENZ ALDEHYDE, 4-Methoxy- 
OCTANAL 
OCTANAL 
OCTANAL 
OCTANAL 
OCTANAL 
OCTANAL 
OCTANAL 
n-HEPTANAL 
_n-HEPTANAL 
n-HEPTANAL 
n-HEPTANAL 
n-HEPTANAL 
ETHANEDIAL 
ETHANEDIAL 
FORMALDEHYDE 

BENZ ALDEHYDE , 4-Hyd roxy- 
FORMALDEHYDE 



Paraform 

Par aldehyde 

Pelargonaldehyde 

Pelargonic aldehyde 

1 , 3-Pentadiene-l-carboxaldehyde 

ii-Pentanal 

1 , 5-Pentanedione 

a-Pent ylcinnaraalde hyde 

Phenylacetaldehyde 

Phenylacetic aldehyde 

3-Phenylacrolein 

3-Phenylacrolein 

Phenylethanal 

Phenylf o rmaldehyde 

Phenylme thanal 

l-Phenyl-l-octene-2-carboxaldehyde 

2-Phenylpropanal 

3 -Phe ny 1 pr opanal 

3-Phenyl-l-propanal 

3-Phenylpropenal 

QKPhenylpropionaldehyde 

3-Phenylpropionaldehyde 

2-Phenylpropionaldehyde 

3-Phenylpropionaldehyde 

3-Phenylpropyl aldehyde 

Phixia 

m-Phthalaldehyde 
-Phthal aldehyde 
Picolinal 
Picolinaldehyde 



FORMALDEHYDE, Para- 

ACETALDEHYDE , Paraldehyde 

NONANAL 

NONANAL 

2,4-HEXADIENAL 

PhNTANAL 

1,5-PENTANEDIAL 

HEPTANAL, 2-(Phenylmethylene.)- 

ACETALDEHYDE, Benzene 

ACETALDEHYDE, Benzene 

2-PROPENAL, 3-Phenyl- 

L -PRO PENAL, 3-Phenyl- 

ACETALDEHYDE, Benzene 

BENZ ALDEHYDE 

BENZ ALDEHYDE 

OCTANAL, 2-(Phenylmethylene)- 

ACETALDEHYDE, a-Methylbenzene- 

PROPANAL, Benzene- 

PROPANAL, Benzene- 

2-PROPENAL, 3-Phenyl- 

ACETALDEHYDE , a-Methylbenzene- 

PROPANAL, Benzene- 

ACETALDEHYDE , a-Methylbenzene- 

PROPANAL, Benzene- 

PROPANAL, Benzene- 

OCTANAL, 7-Hydroxy-3,7- 

dimethyl- 

BENZENEDICARBOXALDEHYDE, 1,3- 
BENZENEDICARBOXALDEHYDE, 1,4- 
2 -PYRIDINECARBOXALDEHYDE 
2-PYRIDTNECARBOXALDEHYDE 



301 



2-Picolinaldehyde 
2-Picolinealdehyde 
PIcolinic aldehyde 
Piperonal 

Piperonaldehyde 
Piperonylaldehyde 

Pivalaldehyde 

Pivalic aldehyde 

Propaldehyde 

1 , 3-Propanedialdehyde 

1 , 3-Propanedione 

Propenal 

Prop-2-en-l-al 

2-Propen-l-one 

Propional 

Propionaldehyde 

Propionic aldehyde 

Propylaldehyde 

Propylic aldehyde 

Protocatechualdehyde dimethyl ether 

Protocatechuic aldehyde dimethyl 

ether 
Protocatechuic aldehyde ethyl ether 

Protocatechuic aldehyde methylene 

ether 

2-Pyridaldehyde 
Pyr id ine-2-al dehyde 
2-Pyridylcarboxaldehyde 
Pyromucic aldehyde 
Pyroracemic aldehyde 
Pyruval dehyde 
Pyruvic aldehyde 



2-PYRIDINECARBOXALDEHYDE 
2-PYRIDINECARBOXALDEHYDE 
2-PYRIDINECARBOXALDEHYDE 
1 , 3-BENZODIOXOLE-5-CARBOX- 

ALDEHYDE 
1 , 3-BENZODIOXOLE-5-CARBOX- 

AL DEHYDE 
1 , 3-BENZODIOXOLE-5-CARBOX- 

ALDEHYDE 

PROPANAL, 2,2-Oimethyl- 
PROPANAL, 2,2-Diraethyl- 
PROPANAL 
PROFANED IAL 
PROPANEDIAL 
2-PROPENAL 
2 -PRO PENAL 
2-PROPENAL 
PROPANAL 
PROPANAL 
PROPANAL 
PROPANAL 
PROPANAL 

BENZALDEHYDE, 3,4-Diinethoxy- 
BENZALDEHYDE, 3,4-Dimethoxy- 

BENZALDEHYDE, 3-Ethoxy-4- 

hydroxy- 
1 , 3-BENZODIOXOLE-5-CARBOX- 

ALDEHYDE 

2-PYRIDINECARBOXALDEHYDE 
2-P YR I D T.NECARBOXALDE HYDE 
2-PYRIDINECARBOXALDEHYDE 
2-FURANC ARBOXALDE HYDE 
PROPANAL, 2-Oxo- 
PROPANAL, 2-Oxo- 
PROPANAL, 2-Oxo- 



Quantrovanil 



See BENZALDEHYDE, 3-Ethoxy-4- 
hydroxy- 



d-Rhodinal 



CITRONELLAL (d isomer) 



Salicylal 
Salicylal dehyde 
Salicylic aldehyde 
Sesqulsulfate 



BENZALDEHYDE, 2-Hydroxy- 
BE NZ ALDEHYDE , 2-Hydroxy- 
BENZALDEHYDE, 2-Hydroxy- 
STREPTOMYCIN sulfate 



302 



Sinapaldehyde 

Sinapic aldehyde 

Sinapyl 

Sodium _o-benzaldehyde sulfonate 

Sodium benzaldehyde-2-sulfonate 

Sodium jD-forraylbenzenesulfonate 

Sodium 2-formylbenzenesulfonate 

Sonacide 

Sorbaldehyde 

Sorbic aldehyde 

Streptobrettin 

Streptomycin A 

Streptorex 

_p_-Sulfobenzaldehyde 

2-Sulfobenzaldehyde 
2-Sulfobenzaldehyde sodium salt 

Superlysoform 
Syr ing aldehyde 

Syringic aldehyde 
Syringylaldehyde 

Terephthal aldehyde 

Terephthalic aldehyde 

Tgtradecyl aldehyde 

A -Tetrahydrobenzaldehyde 

1, 2,3,6-Tetrahydrobenzaldehyde 

Tiglaldehyde 

Tig lie acid aldehyde 

Tiglic aldehyde 

m-Tolualdehyde 

_p_-Tolualdehyde 

jg-To lual dehyd e 

a-Tolualdehyde 

2-Tolualdehyde 

4 -Tolualdehyde 

^-Toluic aldehyde 

a-Toluic aldehyde 

-To luyl al dehyd e 

-Toluyl aldehyde 



2-PROPENAL, 3-(4-liydroxy-3,5- 

d ime thoxypheny 1 )- 
2-PROPENAL, 3-(4-Hydroxy-3,5- 

diraethoxyphenyl)- 
2-PROPENAL, 3-(4-Hydroxy-3,5- 

dirae thoxypheny 1 ) - 
BENZALDEHYDE, 2-Formylbenzene- 

sulfonic acid sodium salt 
BENZALDEHYDE, 2-Formylbenzene- 

sulfonic acid sodium salt 
BENZALDEHYDE, 2-Formylbenzene- 

sulfonic acid sodium salt 
BENZALDEHYDE, 2-Formylbenzene- 

sulfonic acid sodium salt 
1,5 -PENT ANE DIAL 
2,4-HEXADIENAL 
2,4-HEXADIEHAL 
STREPTOMYCIN sulfate 
STREPTOMYCIN 
STREPTOMYCIN sulfate 
BENZALDEHYDE, 2-Formylbenzene- 

sulfonic acid 
BENZALDEHYDE, 2-Forraylbenzene- 

sulfonic acid 
BENZALDEHYDE, 2-Formylbenzene- 

sulfonic acid sodium salt 
FORMALDEHYDE 
BENZALDEHYDE, 4-Hydroxy-3 , 5- 

dimethoxy- 
BENZALDEHYDE, 4-Hydroxy-3, 5- 

dimethoxy- 
BENZALDEHYDE , 4-Hydroxy-3 , 5- 

dimethoxy- 

BENZENEDICARBOXALDEHYDE, 1,4- 
BENZENEDICARBOXALDEHYDE, 1,4- 
DECANAL, Tetra- 

3-CYCLOHEXENE-l-CMBOXALDEHYDE 
3-CYCLOHEXENE-l-CARBOXALDEHYDE 
2-BUTENAL (E), 2-Methyl- 
2-BUTENAL (E), 2-Methyl- 
2-BUTENAL (E), 2-Methyl- 
BENZ ALDE HYDE , 3-Me thyl- 
BENZALDEHYDE, 2-Methyl- 
BENZ ALDEHYDE , 4-Methyl- 
ACETALDEHYDE, Benzene 
BEl'IZ ALDE HYDE, 2-Methyl- 
BENZ ALDEHYDE, 4-Methyl- 
3ENZ ALDEHYDE, 2-Methyl- 
ACETALDEHYDE, Benzene 
B ENZ ALDE HYDE , 2-Me thyl - 
BENZALDEHYDE, 4 -Me thyl- 



303 



-Tolylacetaldehyde 

o-Tolylaldehyde 

-Tolylaldehyde 

Trichloroethanal 

Triformol 

3,4, 5-Tr imethoxycinnamaldehyde 

Trimethylacetaldehyde 

1 , 3, 3-Trimethyl-2-(formyl- 

methylene)indolene 
2,4,6-Tnmethyl-l,3,5-trioxane 
Trioxan 
Trioxane 
^-Tr ioxane 
sym-Trioxane 
Trioxin 

T r i oxyme t hy 1 e ne 
Tylan 
Tylon 
Tylosin 



ACETALDEHYDE, 4 -Methyl benzene- 
BENZALDEHYDE, 2-Methyl- 
BENZALDEHYDE, <f-Methyl- 
ACETALDEHYDE, Trichloro- 
FORMALDEHYDE, 1 , 3 ,5-Trioxane 
2-PROPENAL, 3-(3,4,5-Tri- 

methoxyphenyl)- 
PROPANAL, 2,2-Dimethyl- 
ACETALDEHYDE, 1,3,3-trimethyl- 

A-(2,a)Indollne- 
ACETALDEHYDE, Paraldehyde 
FORMALDEHYDE, 1 ,3,5-Trioxane 
FORMALDEHYDE , 1,3, 5-Tnoxane 
FORMALDEHYDE, 1,3, 5-Tr ioxane 
FORMALDEHYDE, 1 ,3,5-Trioxane 
FORMALDEHYDE, 1,3, 5-Tr ioxane 
FORMALDEHYDE, 1 ,3,5-Trioxane 
STREPTOMYCIN, Tylosin 
STREPTOMYCIN, Tylosin 
STREPTOMYCIN, Tylosin 



ja-Unde canal 
Undecenoic aldehyde 
Undecyl aldehyde 
9-Undecylene aldehyde 
10-Undecylene aldehyde 
Undecylenic aldehyde 
n-Undecylic aldehyde 



UNDE CANAL 
UNDECENAL, 9- 
UNDE CANAL 
UNDECENAL, 9- 
UNDECENAL, 10- 
UNDECENAL, 10- 
UNDE CANAL 



Valeral 
Valeraldehyde 
n-Valeraldehyde 
Valerianic aldehyde 
Valeric acid aldehyde 
Valeric aldehyde 
Valerylaldehyde 
Vanillal 

Vanillic aldehyde 

Vanillin 

_o-Vanillin 

Vanillin ethyl ether 

Vanillin methyl ether 



PENTANAL 
PENTANAL 
PENTANAL 
PENTANAL 
PENTANAL 
PENTANAL 
PENTANAL 
BENZALDEHYDE, 3-Ethoxy-4- 

hydroxy- 
BENZ ALDEHYDE, 4-Hydroxy-3- 

methoxy- 
BENZ ALDEHYDE, 4-Hydroxy-3- 

methoxy- 
BENZALDEHYDE, 2-Hydroxy-3- 

methoxy- 
BENZ ALDEHYDE, 4-Ethoxy-3- 

methoxy- 
BENZALDEHYDE, 3,4-Dimethoxy- 



304 

Vanirom BE NZ ALDEHYDE, 3-Ethoxy-4- 

hydroxy- 

Veratral BENZALDEHYDE, 3,4-Dimethoxy- 

Veratraldehyde BE NZ ALDEHYDE, 3,4-Dimethoxy- 

Veratric aldehyde BENZALDEHYDE, 3,4-Dimethoxy- 

Veratryl aldehyde BENZALDEHYDE, 3,4-Dimethoxy- 

Vetstrep STREPTOMYCIN sulfate 



C B 

O I N^ 

H 

CO CO 

rH M rJCC 

0) O *-> ^ 

> 4-> M S 

P o 6 a 

o ca a. 

CJ ft, -H -^ 



CM 

3D 



s 



o 

X c-l 



C 

CA H 



X) 

I 3 



<U rH O 
> 0) CO 



CJ 
O 

H 

QJ 
C/D 

m 
o 

co 
cu 
H 

4-1 
JH 
QJ 
ft 

S 



t 

cu 

6 



O ft 
Pn o 



a c. 
o 3 
^* o 



I 1 I i 
PH PH 



H -H 
4-1 rH 







CJ 
33 o 



M CO 00 

& CO EC 

CU 01 

ca n 1-1 a 



rH 00 

CM 

r-l O 



CJ 



01 
X) 



I m . o 



00 

o 



m 

o 

7 

CM 



4J ^H 

M H II 

a CO M 

C i-l 

cd 0) co 

> a ^ 



PM 



4J -H O B 



U CO X 00 

fl iH 

CU 01 O M 

O r-l 4-* O 



00 "-. 

r>. oo 



o 

CM o 

r*^ *^ 

CM ^^ 

O O 

. CM 



oo si- 

o -^ 

o o 

CM 



4s 

W 



H 



m 
o 



CO 
CM 



co 
sf 























1 O 


i 












I 






0) 




(L) W 


0) 


CO 




nJ 


I 


QJ 


vO 


01 




C 




C CD CJ 


C 01 


rH 
1 

O 

a 
co 


ALDEHYDE 
3 CHO 


nzene 
acetaldehydl 
C 6 H 5 CH 2 CHO 


rH 
>, 

X 

4J 

I' 
H 

a 
-* 


benzene- 
acetaldehydi 

C 10 H 12 


7-DIraethyl- 


octenyloxy- 
acetaldehyd 


CM 


CM 

i 


Fonnylbenze 
acetic acid 


en 
O 

3? 
CTi 
CJ 


Methylbenze 
acetaldehyd 
C 6 H 5 CH(CH 3 ) 


-Methylbenze 
acetaldehyd 
C 9 H 1Q 


(U 


H X 


0) 


M 




** 






i 




i 


i 


e 


W CJ 


a 


o 




en 






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a 


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305 



P. 00 

6 



CO CO 

h h tJco 

<u o *./- 

> 4- op e 

c y g e 

o co c 

O fc p i v- 



CM 

en 



00 

o 



o 

J3 CM 

3 33 

TH 

O C 

CO H 



XT XI 
00 3 



JC X> 
OQ 3 



H O 
CO CO 



J5 X5 
00 3 



X) 

3 



O 
CO 



XJ 

CO 
Cfl 



O fe, 
(X, o 



oo oo 
c c 

H H 
tJ i-H 



O U 

cq o 



in r- 
I en 



CM 
l 



m 
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CO 00 

ro n: x 

01 o 

t-i jj S 

0, 3 6 



o 
m CM 



a CO H 

C -H 

ca <u eo 

> Q s_^ 



4-> -H O 
r-l 4J cvT^ 

co cd K oo 



CM 
O "-> 



O 



O in 



CM O 
. CM 



CN 
CM 



o 

CM 



CM 
CM 



13 
0) 

a 
rt 

H 



o 

bH 

a 

(0 
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e 
cd 

55 



O 
O 



DEHYDE 



e 



s - 



cu 

g, 
5 -g 

XT CU T3 

C f-J 

<U crj 

N U 

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0) CJ 

XJ cd cj 
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xTo 
cu -^ 
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td 
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1 




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TJ 


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>> 


W >, 


Xi 


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1 QJ 
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E c cu o 

H -H T3 3 


M ~| K 


M 1 rH u" 


CO CJ 


f-'^Cd - 


r-l 4J CO 


1 8 W 5G 


x: cu H 


CO " CU f 


U 


~cM O " 


H cj 


CO N-X cd O 


j-i 


M 


E- 


F-H 



g 

So 

3 

J m 

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M vO 

K CJ 
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OQ 




306 



30 

en 



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vO 



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3 



XI 
3 



XI 
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r-l 
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C 



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M D 



r-l O 
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>> i 





m 

_f 

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CM 



CM 
00 -s. 

O r-H 
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CM 



oo 



csi 

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fi 

CM 



/~\ Ol 

o -a 

C rSO 

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c| 13 O 

rH rH CM 

^1 Cd rH 



4-1 
01 
O 

C 



o -o 
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* 



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xi 

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307 



a oo 

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o 


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c u S a 

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r^ OJ 


i-H 01 
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... ^ *Tn ^ 


X- ^ 


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H J 2l 


00 3 


00 3 


00 3 


C 
C/> iH 


HO HO 1 | 
CO CO CO W 1 | 


^ ^ 
H 
1 CA CO 


H H 
H 
tt) CO 


rl H 

rH O 

C/3 CO 


ca C 










ed iH 

rH tn 
tti PU 


i ! ! 


I 2 

1 rH 


1 
1 


1 


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4-J -|J 










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M 60 


CO 


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CO 


M C 


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4-1 rH 




\ OH 




H 


rH iH 

fl) O O 
Js 03 


1 1 jQ 

j^- <t p 1 I 


1 f^ 3\ ft, 


O -* 


-i 3 




'n i i 


1 | -H ^ 


-t CM 




1 










h co 00 

o to .3: /-N 

fti 01 01 U 




Jon 


rH 

vO 


rH 3 

CM r-x 


cd f-i n s 


! ! ' ' 


rn ON 


^ 


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f 1 " 3 v-- 


iiii 


! ^^ 


O 


rH O 


t 




CM 


CM 


i-H 


4J rH 










H -H || 
&CO t-l 
C H 










> Q s-> 


iii: 


. 
l -4- 


1 
1 


2 


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/-s 


>-, > rH 




s~\ 




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o 


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^ 




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w cd x to 




p*^ <f 




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CN O 


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i i i i 


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. CM 

1 rH x- 


1 


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00 i-H IT) ON 
^ CM CM -H 


r-. co 


o 

i l 


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CM 

CM 

r- 1 


CM 

CM 

i-H 


TJ 










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H ^ 1 1 S 

S 1 o o SSo 
r9 cdrrt-, ^ <uo33oj-a 

1 - 11 SI -f*^ su 

E S t-^ ? n .^^ S " 

-r | 1 ts^ ^-So^ r g^ JS^ M 

I ^ ^ S*"I3 O frrHjNrHiW/^ i-HC^J 
"^ T3 S OM3S5jT < b lH:i! >.OO 
C J -Cria^ 32^-. 03CO S4Hv_- 

Cd a 3 "SS* ^coficoo ErHST 

I 1 ?-^ ?-cT ^^ g - 

< I " * -* N 


2-Fonnylbenzene- 
sulfonic acid 
sodium salt 
C 7 H 5 Na0 4 S 

2-Hydroxybenzaldehyde 
C & H 4 OHGHO 


3-Hydroxybenzaldehyde 
C 7 H 6 2 


4 -Hy d roxy b e nz al dehyde 
C 7 H 6 2 



308 



-? 1 


-H 


O 




CO .0 1 


) 


30 




( -H 1 




( 








0) 




s*, >> 


>-. 


iH 




-H CU rH 01 


^ Oi 


X 




4-1 rH 4-1 -! 


4J i 1 


3 
,_4 




00 3 OC 3 


oO 3 







H iH i-l i 1 


H ^1 


co 




-HO i-H O 1 


^H O 


c 




CO ID C/2 CD 1 


C/3 CD 


t 








sf 




1 1 1 


1 


-a- 




1 1 1 


1 


CM 




l-i 








CO P .O 






o- 


O"\ O ^^ >>O 


***^ 


"x^ 


*^ 


i jj in -M 


co 


00 


CS 


**^ 1 *^" 1 


00 


CO 


I 


co tN <r I m 


1 ""* 


1 


ro 


1 O\ H -3- -O I 


1 


r*^ 


^ 


"I 1 s ' <J" "\1 1 


OO CM 


CO 


'M 


x-\ 

00 


x^ x^. 


X-N 






r~ O 


m 




1 1 


O P~- 


CM 




XX 

1 1 


x-< v-X 


N_X 




1 -H 1 


i m 


30 

-H 






CM 






1 1 1 





1 




1 1 1 


m 


1 






u 





/-N 

O 




m 


CO 


-^. 




o 


r I 





1 1 1 








CM 


1 1 1 


" 


-H 


~ 


I 1 1 


vO 


vO 




CN CM 


CM 







oo m i 


in 


co 




i i i 


"" 


r 1 




0) 




CU 




-o l i 


1 


o 






> O 


^ 




XX X 


X i 


X 




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U 


cu 

t: 




T3 iH 4J 4-1 


4-f "T* 


H 


O 


I co QJ cu cu a) 
m N g -a 6 -a 

C 1 >* 1 >-. 

CO CU CO X * X 


0) 01 ^O 

6 TJ ;j 


H 
111 


33 
co 


IX 1 CU 1 CU 


i "aj o 


X 


33 


>i >> -^" >^ T3 >> "O 
XXO XrHCO Xi-{ 
OOO OcflO OC6 
l-i X I UNOO ^N 

*"O -^ *T^ *^J ^ *T] ^Q j 

>~iCU^ S^CUSO >><U 
X60 =3X0 33X 


X "H X~N 

CO 
l-i N CO 

a c 33 
> cu u 

33 X ''^ 


Methoxy 


O 

vO 
O 


1 1 1 


1 


i 




~* <N fo 


<! 


CM 





-< O 

CM 



vO 
CO 



CU 
T) 

X 
cu 

r-H O 

id 33 

N U 

C s~* 

QJ CO 

>> CJ 

X O 

O - ' 

X j* 

(U vO 

S O 
I 



O cs| 



CU 
T3 
^ 
CO 
N 
C 
CU 



^ co 

H CU Q) 

4J -H X 

00 3 X 

H rH 4J 

-( O H 

C/> CO ? 



vO 
CO 



O CT 



o 

CM 



0) 

I 

01 
T3 



00 
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CU 00 



309 



H4 

O. 00 

E 



C 
O 
1-1 

09 U 

(-1 U JfO 

01 O -v. --N 

> U 30 

c u E a 

o co a. 

u tx, - v^ 



o 
eg 



CM 

oo 



CM 
oo 



o 
ro 



en 
m 
m 



Ol 

sa f 

iH 
O B 



rH 01 
AJ rH 

x: -Q 

00 3 
H -H 
-I O 
00 CO 



H 0) 
U rH 
JS XI 

oo 3 

H rH 
H O 
CO (0 



x: xi 

60 3 



rH <U 

U rH 

X! XI 
00 3 

H rH 

H O 

CO CO 



x: 
ao 



rH O 
CO CO 



>-, 

rH tt) 
U -H 



rH O 
00 CO 



0) 

rH 
JO 



o 

CO 



x; w 

u c 

CO -rt 

H O En 

[IH P-. O 



PH PH 



M (0 00 

&n > 33 <<4 

01 01 o 

C8 r-l ^ S O 

> O, 3 i v-/ 



7 

* m 
I co 

I CM 



30 O 
-^.^4-1 
O CM 

CT> I -H 

I m r>. 
o\ *$ r*. 

30 CM ' 



!->. 
<=f 

CM 



CO 
fM 



CD 

cr> 
I 



o 
eN 



aU) 
c 



CM 

LT| 



CO 
st 



" 01 
>> > 



H 4J 



o a 

CNT^. 
cd 33 60 



U 
Ch o 

oo ^r 



o 



in 
m 






C 

01 0) O 

a M 



CM O 
CM 



O o 



00 O 

CN 

O ^ 



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S 3 



T3 
QJ 

3 

d 



w 

r-l 



o 

CM 



01 

I 



CM 

to 



rH 


1 


l 

id 


r-l 

CO 


3 
B 
-i 





2 
a> 


N 

01 


O 

Ex 


JH 

X 


Xt 
H 


Xt 
r^ 


a 

c 

C8 



3 


X 

x; ao 

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Q) 00 


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l> S * I-'CM 

I 8 Ig"l B 


r2 ' 


1 


C| 


ON 



OJ 


H 




TJ 


XI 




^ 


3 




pC 


U 




01 






TJ 


rJ 




a 


01 

a 




m 


CO 




o 






c 


r-l 




o 

H 


oo 

H 




H 
H 
B 


rH 
H 

B 




M 


c 

H 




. 


C 




CO 


o 




t-J 


4J 




cd 






a. 


^ 






4J 




o 


0) 






CJ 




i^ 


C 




0) 


o 




rQ 


CJ 




B 






3 


cd 






o 




01 






JS 






u 


4J 




o 


01 




4J 


rH 






CO 




U 






C 


H 




0) 


3 




rH 


cr 




cd 


01 




H 


CO 




3 


H 




cr 






01 


^^ 




CO 


S 




H 


CO 




0) 


i-H 




T3 






J3 


CJ 




01 


O 




nQ 


m 




1 


CM 




O 


H 






CO 




c 









B 




H C 


H 




I 


OI 




r-l rH 
4J O 


"?, 




C 






0) 


01 




O CO 


o 




C -H 






X 


CD 




O 4J 








01 




C C 


ij 3 






3 




rJ B 






0) 3 







W 


CJ 




H X 


B 




rH CO 


O CO 






H -H 




j -i^ 


^H *C 





oi B 


nH W 


^ 


a w 


H 


4J 


ca 


B B 


H 


I-H 


M 


cd 


r-l 






M 


& 3 


(xO 


H CJ 


Q 




rH o 


4J X 


CJ 


rH m 


r-l CO 


H 


H CM 


CO 


4-1 


S ^^ 


a M 


H 




01 


CJ 


0) r-l 


0) iJ 


01 


d -H 


B 0) 


0. 


^^ fl 


B 


CO 


cd 




U 



318 



CO 

a) 

! 



O 




co 




1 rH 


4J 


CO cfl 


c 


O " 4-) 


CU 


H rH C I > 


50 


4-1 O 0) CO 01 


cfl 


0) C P- > C 


01 


co ' cfl 


M 


cfl w a 




3 01 - O 


ts 


TJ 43 TJ >H rJ 


l-l 


rj | -H CO P. 


O 


Cfl C| l-l rH 
1 CO 


4J 

cfl 


TJ H rH 
H Ol O 43 >i 


O 


O TJ H tJ -3 


43 


Cfl >, 4J 4J 


CO 


^: cu cu 


rH 


U Ol O CO S 




H T> (0 OJ -H 





4J ^H H C U 


aO 


cy cfl o) H w 

O O. TJ 


C 
H 


CO rH H 


M 


>> t-l rH 


O 


m _** rH ^ o 


^ 


O 4J O P. O 


cfl 


01 C >. CU 


rH 


Ol CO rH 4J 


4H 


U X rH bO CO 

3 01 3 H 
4J TJ 43 4J OJ TJ 


CO 


O H rH H O CU 


d) 


CO Vj >, J-l 0) S 
M-l TJ f 43 rH H 


3 


3 >, 4J 4J >, 01 
G J! Ol 5s 4J 4J 


H 
M 


rt ^ 1 l-i 3 S3 


01 


Z cfl CM CU 43 -H 


^ 



if 

H 

rJ 
O 



PS 


T^ 


o 


5s 


c 


43 


>. 

C/3 


01 0) 
TJ <U TJ 
Ss TJ rH 


TJ 

a 


43 X Jfl 
01 43 Q 
TJ CU M 


cti 


H TJ 

^rH^ 


CO g. 


O CO rH 


^ a 


iH (3 rH >% 


CO o 


*J CO tS43 


P c 


01 J3 43 4J 


>s 

en 


CJ 4J 4J QJ 
< W W S 



CM 
I, 



W 

3 



o 

D. 

e 
o 

CJ> 



rJ 
01 

43 



Z 

o 





(-1 


CO 








01 


e 








TJ 


CO 








<U rH 


o 




01 




^3 CQ 
n) t>% d 


0) 


T) 


T) 

?> 


Phenylacetaldehyde 
Benzeneacetaldehyde 
Hyacinthin 
Phenylacetlc aldehyde 
a-Tolualdehyde 
a-Toluic aldehyde 
Phenylethanal 


2-Methylhydratropaldehyd< 
2-Methylhydratropicaldeh; 
2-( p-Methylphenyl) propio 


Citronelloxyacetaldehyde 
6, 10-Dimethyl-3-oxa-9-un 


a -Fonnylphenylacetic aci 


Hydratropaldehyde 

TL -Phenyl pr opanal 
2-Phenylpropionaldehyde 
ct -Phenylpropionaldehyde 
Hydratropa aldehyde 
Hydratropic aldehyde 
Cumene aldehyde 
Hyacinthal 
a-Methyl-a-toluic aldeh: 






i 










in 

>1 






cu 


L 


{3 
0) 






TJ 

Ss 


S 


4-1 
O CU 






43 
01 
TJ 
rH 
CO 
4J 
01 
O 


M 

0) CU 
43 TJ 

12 
fl-S 


thyl-b-o 
taldehyd 


benzene 
acid 


&> 

C3 CU 
4) TJ 

8 

CU 0) 
43 TJ 


CO 




0) oi 


rH O 


rH rH 




a ffi 


s o 


Ss-iH 


>. 


s 


iH 4- 
3 01 


5 CO 

Q rS 


gS 


43 W 

4J Ol 


0) 
N 

C3 




T * 

t-. o 




fn CO 


CU U 

f * 


CU 
PQ 


a 


co" 


8 


8 




CTi 


CO 


7 


00 
1 


00 


CN 


vO 


00 


CO 


P^" 


1 


| 


1 


1 


CN 
CN 


S 


CN 

CTi 


vO 

i I 
cN 


S 


-H 




^ 


ON 










in 





319 











CO O 


" iH 










* 


T3 










l-i -H CU 


CO M 










bo co 


H 










OJ C C 


G 01 










G H CU 


U . 










rH Cfl H 


iH TJ 










H O CO 


CO (0 CO 










O) 60 O 


CO 










to Xi O 


*> 0) H 










O h H 


OI 01 










O O rH 


CU B O CO 










O O TJ 


l-i 00 




e- 






> O 3 


4J 3 t-l O 










Cd O) 


o 




3 






CO rH rH 


cd VM o -H 










U 


* 1 I 




^^ 






-H CO rH 


rJ IN! N B 










OJ 4J .. 


CO 3 

B rH 




TJ 






*4H O) 
U O 


4J CU C 0) 
H Q. 0) X 










O 0) M 


3 rH 




G 






-H 


C Xi U 










XI X 01 


M 0) 




cd 






CO U 0) 


o 










3 4J W 













<u cd 


TJ H U 










>-l C CO 


* 




01 






rX B O 


B -U TJ -H 










r** *rH 


00 )-l 




4-1 






TJ O CO 


cd cu -H x; 










- CO TJ 


01 O 




cd 








x: o a 










0) 01 


X 4-1 










M ed * 


CU 4-1 Cfl tfl 










"O B 

>, to C 


3 CO 




TJ 






O CO 


4J G h 
to P~i U M 










X! 4J 0) 


CU 




XI 






2 -H 


4J CO -H Q 










0) C 4J 


ft ^J 










01 CO CO 


CU 4J 










TJ Cfl G 
H TJ -H 
CO H 


CO 3 

rH 4J 
H X 




1 






4-1 CU 
CO CO P 
r-l CU 


o cd o 
co co c x: 

TJ G a 










4J X 4-t 


H 




o 






TJ 


0) C -H 










CU O 4-1 







rH 






OI 3 CO 


CO 3 O 










H ''I 3 
Cg W | E 

G CO 


* 
CO 4J 
4J C 
CO 01 


01 

H 
4J 


U 

4-1 






eM-l rH 
M -r4 
OI OJ O 
4-1 fr. 


O O O 
rH CX4-I rH 

3 B O cd 
i 1 O O 










O >> 


4-1 > 


CO 









G H 


i 1 O CU H 










4-1 M TJ 
CU 
01 XI 
4J Xl CO 


rH 

u o 

O CO 


TJ 

CO 


0) 

3 






H O 
CO 4-< 
rH rH 
CO fO 4J 


01 t"l 4J 

U M 3 3 

C 4J CU 

-H O U 










3 3 -H 


*> 


* 


4-) 






-H d 


Cfl l-i Cd (0 


u 

0) 








4J -i Cd 
H U 


4J tl 

G 01 
CU X! 


CO 

CU 

t> 


O 

cd 

4H 






H M OJ 

01 > 
4J rH 


M o 4-1 a 

(U > 3 C 
X! cd G cfl 


co 








CO CO S 

Xl rJ (U 


> 4J 
rH CO 


H 
4-1 


g 






62 o 
CO 


U rH ffl JO 

cu 4-1 g a. 










3 o x: 


O OJ 


CO 


[rt 


















CO 4J O 


CO rH 


> 


s 




1 
























CU >> 
























c x: 






















cu 


CU 4J 






















f> O 


rH 0) 














CU 








^^ 
















c 








i x: 


XI -H 








(U 






oj 








rH CU 


4J rJ 








T3 






X 








>.TJ 


01 4J 








(1) >t 






o 








X! rH 


1 








*o c 




CO 


H 








4J CO 


rH en 








l^\ O 




rQ 


^ 








OI 4-J 


>-, 








X! TJ 




5s 


4-> 








a cu 


Sen 








CU H 
TJ crj 

rH 4J 


1 


XI 
CU 


1 
m 

ft 








H U 
t-i co 

4J 1 


. 

O -H 

4-1 | 


9) 


rH 




oj cd oi 




H 


cn 












!>. 


n 


Synonyms 


p-Tolylacetaldehyd 
j>-Methylphenylacet 
(4-Me thylphenyl) ac 


(j>-Isopropylphenyl 
acetaldehyde 
Cortexal 


j>-Cymene-7-carboxa 


2,4,6-Trimethyl-l, 
^-Acetaldehyde 






Chloral 
Anhydrous chloral 
Trlchloroethanal 


(l,3-Dihydro-l,3,3- 
2H-indol-2-ylidene 
Fisher's aldehyde 
l,3,3-Trimethyl-2-i 
indollne 
2-(Formylmethylene^ 
indollne 


Benzenecarbonal 
Benzenecarboxaldeh; 
Benzoic aldehyde 
Phenylmethanal 
Artificial almond < 
Benzaldehyde FFC 
Phenylform aldehyde 






OJ 






















s~* 


G 




eu 





















OJ 






















T3 


N 




^. 






0) 












4J 


G 




x: 


















O 


01 
Xi 




3 






X! 


i 








TJ 


U 


r7 




d 






01 
n 


< i, 








Continued 
Name of Compoun 


(ACETALDEHYDE - 

4-Me thyl benze ne 
acetaldehyde 


4-(L-Methylethy 
acetaldehyde 




Paraldehyde 
(trimer of acet 






Trichloroacetall 


1,3,3-Trimethyl- 
(2,a)-indolin 
acetaldehyde 




BENZALDEHYDE 




OJ K 
1 0) 


vO 

i 


o 
i 




i 






1 


? 




^ 




<j Xi 

i 


01 


CM 
0\ 




en 
sO 






1 

00 


1 

cn 

00 




CM 




M r| 


' 


1 




l 






1 


1 




| 






T^ 


"i 




cn 






L/*J 


si- 




o 




M OT 


o 

i 


en 




CM 

i i 






rx 


oo 









Fi ^J 

























320 







i 

o 

c 

H 


1 

o 

c 

H 

i 






01 

a oi 
>, C 

JZ -H 




rH 
r-4 !>. 

Is 

O 0) 


dime thy: 






0) 0) 






g 


iu 






01 1 




Q 5 


n\ 






-a -d 


o-Chlorobenzaldehyde 


j)-Chlorobenzaldehyde 


4-((2-Chloroethyl)ethyla 
o-tolualdehyde 


-((2-Chloroethyl)methy] 
benzaldehyde 


l 
1 


1 


p-(Diethylainino)benzald 
p-Formyl-N ,N-diethylani 


1 


Veratraldehyde 
3,4-Dinethoxybenzenecat 

Protocatechualdehyde dd 


ether 
Protocatechuic aldehydi 


ether 
Vanillin methyl ether 
Veratric aldehyde 


Veratral 
Veratryl aldehyde 
Methyl vanillin 


p-tert-Butylbenzaldehy 
"4-tert-Butylbenzaldehy 
















0) 


01 














i i 


i 

i-H 


1 


01 




-d 


">, 














rH rH 


>^ 


rH 


g| 




js 1 


fi 








JL^ 






> cd 


42 


p 


jC 


i 


0) 


01 








H 






.fl N 


4J 








d 


-rj 










0) 

-d 


i 


4J C 

01 01 


01 0) 

j3 -d^ 


4-1 01 

oi -d 
S >, 


01 

rH 
rrl 


0) 


rH 

cd 

N 


i-H 

cd 

N 








4J 

01 




j- 


I-H rH 


rH J2 


^^ rC 


w 


'^ 


ri 


d 








^j 


Chlorobenzaldel 


Chlorobenzalde] 


((2-Chloroethy 
amino)-2-methy 
dehyde 


((2-Chloroethy 
amino)benzalde 


-((2-Cyanoethyl 
amino)benzalde 


, b-Uichlorobenz 


-(Diethylamino> 
aldehyde 


,5-Dimethoxybei 


,4-Uimethoxybei 








rn 

S G 

1 (1 

1 t" 

M C 

rH C 


i 


i 


i 


i 


i 


CM 


sr 


CM 


co 










CM 


^r 


"* 






















m 


i 


^ 


m 


CO 


m 

1 


03 

l 


| 


T 








1 


l 

CO 


i 


o 


l 


l 

i i 


00 




CM 


;* 








ON 




X> 


i 


n 


CM 


CO 


CM 
| 


T* 


1 








1 


o\ 


i 


CM 


l 


<r 


1 

CO 


O 
cvl 


S 


O 
CM 








li 


-O 


o 


er* 


c^ 


CT> 




i-H 















321 









cu 






d 






3 
H 












^i 






H -d 






T3 












CO 






-H 






O 


U CU 


Ol CO CU 








F-l 


cu 




cd u 
cd 






CO 


cd cd 


cd cd cd 








>, 


^ 




o 


d 


d 


^ 


CO Pl 


PI e PI 










j3 




i-l U 


H 


H 


f-l 





o o o 








y 


01 




P! -H 


u 


U 


a 


a 4-1 


W <W M-l 








01 






o c 

<4-l O 


cd 


cd 


cd 


1-3 


5^^ 








cu 
d 
>, 


N 

c 


CO 

d 


H 0" <* 
3 -d H 
CO >> 3 


o 

H 

G 


T-t 

P! 


a 

C 


d co 
I 
CO CM 


CO CO D) 
CU CU 
Pi C CU 




cu 






01 


x: u 


H X! CO 


O 


O 





1 


cu cu 'd 




d 

x; -d 

cu >-. 




CO 

d 
H 


X) 
X 

o 


Ol 01 
"O XI 

rH 4J 

cd a> 


d 0) -H 
CU T) -d 
CHI 

01 Cj) ^ 


01 M-* 01 

d H -d 

>, 3 >. 
X! CD X! 


(0 


M-l 
CO 


CU <U 
TJ T> 
>, >^ 

-P! x: 


SS 

Q) 0) Q) 
-Q XJ T3 


Synonyms^ 


jr-Ethoxybenzald 
Ethoxybenzaldeh 


Bourbonal 
Ethavan 
Ethovan 
Ethylvanillin 
Vanillal 


Vanirom 
Ethylprotal 
Quantrovanil 
Protocatechuic 


4-hydroxy-3-eth 


4-Ethoxy-m-aru.s 
Vanillin ethyl 


4-Formyl-m-benz 
2,4-Disulfobenz 
Benzaldehyde-2 , 


2-Sulfobenzalde 
o-Formyl benzene 
o-Sulfobenzalde 


CO 

01 
N 

Pi 
01 
XI 
H 
>, 

g 

Ct, 

1.1 


sodium salt 
Benzaldehyde-o- 
salt 


2-Sulfobenzalde 
Sodium benzalde 


Sodium 2-formyl 
Sodium o-formyl 
Sodium o-benzal 




^^ 












o 


u 










d 










l 


H 

C 


"c 










4J CO 










CO 


o 













C -d 


l 






i 


ti 














cS J? 


x 








0) 

N -d 


H 


H 


rH 






"S 


. -S 


g 






1 


C H 

cu u 


CO 
CO 


CO 
0) 


cd 

CO 






3 


H 


d cu 






4J CO 


xi cd 


P! 










O 


[d cd 


^"1 ^3 






CO TJ 


| 


CO 


Q) 


ri 






a 


Q y 


XI >, 






B r^ 


CO O 


N 


N 


3 






*cl 5 


fc B 


i x: 






i x: 


-H 


Pi 


Pi 


H 






U CJ 


cu 

W rQ 


* cu 






CO CO 

1 -d 


-H Pi 
1 O 




CO 
XI 


-d 

O 






C 14-1 

H 
4J 


1 1 

N X! 


xl 






O N 

x: a 


E3"3 
G co 


H 

gs 


g 


3 






a si 


Z 4J 


4J 0) 






4J CO 


O i-l 


O 


O 


o 






T* S 

o 1 


Cd Cd 


Cd f 






Cd XI 


ta -d 


h cd 
1 


1 


cd 






^J 1Z 


^ -<r 


CO 






st 


"* 


CM 


CM 








oi M 


o 


^. 






CM 




CO 


vO 








<J XI 


CM 


i 

CM 






1 

m 


7 

CTi 


1 


1 
CM 










00 


CO 






CM 


fO 


CM 












1 


1 










1 


1 








Zj 5S 


H 


i I 






o 


CO 


I 


00 








S9 <2 

*s < 




o 


CM 

-H 






CM 


CO 


0> 




O 








H 

























322 



.. e 

&T! 

4-1 Cd 4-> 

co s a 

H 3 cd 
O 00 



OH rH 

x: a cd 

o 4-1 9 u 

O UH -H 



al 



co >s D 

O H M 0) 

H co ed O 

4J CU iH Cd 

J*. X! rH B 

rH 4J H fi 

iUl -S 

<J CO Cd OH 









01 

1 

U CU 
CU 0) TJ 
C X! rH 

cu 4J cd 

NO) N 

d ri 

CU <H Q) 
Xt > XI 
> X! >, 


cu 

^ 

x: 
cu 

TJ 
r-H 
CU (U Cd rH 
O TJ N O 


cu 

TJ 








X 4-t X 


>. ^ Pi C 


^ 


cu 


cu 


01 


O CU O 


x: x: cu cu 


XJ 


TJ 


a 


TJ 




eu cu xi xi 


cu 


^S, 




^\ 


TJ *H "t3 


TJ TJ r^\ (X 


TJ 


x; QJ 


Xi 


X! 


>^ "t3 ^s 


rH rH pS r*^ 


H 


cu n 


cu 


cu cu 


x: i cu x: 


cfl (d o X 


cd 


*^J r^ 


TJ 


TJ TJ 


1 10 TJ CU 1 


CO rH IH rH O 


CO rH 


CU rH X 
TJ Cd CU rH -H 


73 rH rH 


cd rH x: 


1 en CU XJ >% 1 


H >-, T3 O X! 
ti >, 4J 


3 S 


> N TJ O O 

x: a -H e e 
cu cu cd cu cu 


N O O 
fi C C 
cu cu cu 


y o a) 

e a -o 

<U CU rH 


>, TJ CU X! f"> 

X cu !>^TJ cu X 
O TJ X! H T3 O 


CO -H Xi g 

si"^ -M cd r 


cd cd 
L -H 
fX) ed CJ 


TJ XI X! X! 

H >i in o cx ex 

cd X CO ,H H -H 

rH O rH rH >, >, 


Xi X! X! 

>s a. a 

8 * 


X> X! ed 

&.5-S 

o >, cu 


x! H >, cu cd rH x: 

4J cd xi T3 ed 4J 

OJ C CU rH O r-H 0) 

B TJ cd -H >. I 


r Cfl I 3 C CM 

^.T^^r^rH 

O O O 5s H !>i 


b a " 

X rH rH 

O rS H 


rS h >> >, B E 

O TJ U C C 
H >, H H O O 

rH 33 H rH EH fcj 

cd I cd cd I i 
co o co en o CM 


.s e s 

> o o 

53 h fe 

klfelA 


H S XI 
TJ C >, 

^fi 

JX|fX|rX| 


H XI rH t)0 M 00 3 

Q H ed C d C O 
1 ed rH -H -H iH 1 
m cj H H JH H m 
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lill.siaifci.al'ls 



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Synonyms 




a-Pentylcinnamalde 
a-Arayl-3-phenylacr 
a -Amyl cinnamaldehy 
Amyl c i nn amald e hy de 
Flomine 
Jasnunaldehyde 


2 , 6-Dimethyl-5-hep 


Sorbaldehyde 
Sorbic aldehyde 
1 ,3-Pentadiene-l-c< 
2,4-Hexadien-l-al 


CO 
73 
Qj >. rH 

T3 CO j=! H co - 
> CU 73 Qi co d 
.C 73 X 73 d S 

73 11 . J3 rH CU I < 

>%73^CU <U CO XCM, 

s -^ -p s i < 

aJCd73rHrH>, (J XX3 
T3 H Cd Cfl J3 ^ | CU 

rHyrdodcu d CMS^ 

CO H d p CO 73 D l| 
OOOQ-XrH rH COCOC 

M t-i j-i cd <u co >, ddi 
aaaosx x cococ 

ucS^tic^ s si: 


2-trans-Hexenal 
(E)-2-Hexenal 
Leaf aldehyde 

Isodihydro lavandul 
2-Isopropylidene-5- 
















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2-Hydroxy 
2-Hydroxy 
2-Hydroxy 



y d r oxy - 1 
ydroxynap 
orm-2-n 



y 
aphthol-i 
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e 
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ehyd 
ldeh 
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c al 



oic a 
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g 
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2- H 
2-H 
1 -F 
2-N 
B-N 



onald 
-Nonal 
-Nony 
onyli 
onan 
elar 
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tral 
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r ani al de hyd e 



, 
cu 

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^ rf )^ ^4 f I r-n *>* M *4 l^ VAI ^^ v *^ ** 4^ %-^ ^^ *^ u *- 

I I o o a) a) HOICU cdcdi oouui I I ,H f-1 
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00 

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333 





ery (fixative, muguet odor), 
ing, soap and cosmetic fragrances 


Lng agent, fragrance 




ng, rubber accelerators 


cd 

e 

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a 

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CO 

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M 






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H 
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CU 




onyms 


roxyc itronellal 
-Dimethyl-7-hydroxyc 
fd roxyc itronel lal 
ronelial hydrate 
Lalia 

Losia 
,1 


CU CU H h 

o t> o cd 

>> >i to <J 
<U 4= JS 1 

H cu m cd CN 

<i T3 T3 rH I 

H r-t rH >.. flj 

00 fl C C 

H c s cu cu 

4J -H CO CJ J= 4J 

cu to a ^ a o 
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w -H >, ^ S;,H 

S ^^^ xo>, 

C 4J 4J Cd (U QJ C 
3 TJ "i S{ SB 1J =3rH^S 


Idaldehyde 


R 
s ^ 

H " 

T3 cd C Q) 43 T3 
>.CO CU T3CUCUr-| 
43CO-H T3 >, T3 -Tl d 

QJ a a cu >, 4= 3 >, 

^Op T045 OJC043T3 

THSfe ^^ " <U^ 

rtaa x!T3 -HOTSOrH 

^5 && ^-a ^7j fl s 

^|a 1 3S7j4i5 1 ii53 


:hylvaleraldehyde 
:hylpentanal 
nnylpentane 


c 


^ K^ F^ 1 II \, 

> - 1 H fs & ! 
a en r^ o rj c_j & 


JJi>^33M | &-.IX! 

5 S ^ s? fip" 3 ci 5? tift; 

H T^ 3 3 J3 | CU 1 1 
Hi-JJSS^, 83JQ-H 


o 

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^^J^J, CUCflcUCUCUCUOJOJ 

>,-Henen r-j> I _| HrHrHr j OL( 
pHO,.. cO| cOcdcOcOcoi 
O H CM CN > c|> > t> > > qjl 


OJ ^ 
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j 




H 


o 


O !* 


?s 


3 






o. 


U 


,JM 


^^ 






^j H 

CD o 


1 ? M 


4J 
CU 


O 

CQ 




cO 
u 


fl ^ 
H o 


<j o c 


g 


U 


J 


cu 

a 

H 


4J 


2 *a ij 


cu 


j2 


s 


> 


(H CU 


EH >, /j 


j^ 


<G 


2 


u 


o 1 


S 2 


Y 


X 


E-. 


cu 






CM 


o 


&J 


1 

CM 


CN 












1 nj 
<1 J3 


1 


f 


1 


T 


a. 


H | 


1 


vO 
00 
1 


<n 


1 

CM 
vO 

1 


i 


3 < 


o 

i 


O 
1 


vO 

r*. 


o 

1 1 


en 
CM 

i 



334 



>, CO 



W 43 Cd 



U M iw 
-HUG 
d H ^ 
O 4J CO 

H co -H 

O. Cd T) 



> 
d043-H 





01 








Ol 
T3 


0) 
CO TJ 


01 01 01 

X-O 42 43 43 
(U 42 >, r-j OJ Ol Q) 

>,TJOITJ CrH,-jrH 


1 

H <U 
>>TJ 

4J 43 
0) CU 


rH 
rS 0) 

3 >> 

1 0) 


CU 
TJ 

01 


01 


<"{ 




CU 






TJ ts 




e 


TJ 


4J ^} 


CU TJ 


TJ 


01 




d 


0) 


43 




01 cd i i 43 cd cL d (3 






M rH 


TJ H 


CU >> 


TJ 




o 


TJ 


0) 


43 01 0) 


TJ CO 0) d O O rH O 


a 


cd 


u cd 


ts cd 


TJ 43 

>> Ol 


rH 

cd 




H 
TJ 





TJ 
01 H 


0) TJ TJ 
TJ X r-l 


r-JOSTJCOH-H>s.H 
cd-H COrH 0.0,0,0,0, 


rH 




v^ CD 


01 43 4J 
TJ (U CU 


43 TJ 
CU H 
TJ ed 


H 
TJ 




CU 

d 
cd 


0) 

TJ 
r-j rH 


TJ Cd 
5s 
43 


H 43 Cd 

cd cu w 

TJ 01 


a g d CD o i o o o 
dd-HOia.| 0.0.0. 


3 


d 
d 

H 


HI 


>, TJ O 
43 H Cd 
01 CO rH 


rH rH -H 

ed cd TJ 

I-l W r4 


O 

d -H 
cd t-< 


X 


0) U 

TJ d 

H Q) 


cd cd 
d d 




0) -H 

a d 

I-) O 


U H U 

H cd cd 

rH H rH 


d d O CJrHrH'HrH'H 
HiH O Cd >%^>>^>%>^ 


CQ 
1 
4J 


o 
o 

r4 rH 


rH O 

b 

H 43 M 


TJ fs 

rH 43 
cd -H 4-1 


cd cd cd 


co cd 


0) 


U CU 


H -H 


Id -H 


>. rS >. 


O O TJ ^ 0) CU Q) CD Ol 


M 


TJ Cd 


CO 4J TJ 


rH rH 0) 


4J 4J 4J 

_g => 3 


0) 4-1 

a 3 


a 

CO 


2 ' 

d m 


a o. 
o o 


a a 
o o 


O. O.43 

O O 4J 


M U S^NJ342424343 
TJTJ43 dPMpLiCLipLirii 


0) 


&-H 

43 H 


tsj} >, 

>H S 43 


cd cd S 

> > H 


1 ( 1 ( 1 

U 


33 





o - 

U5 rH 


W M 

DH en 


rJ H 

ex, a, 


H U Q) 
BU (Xi S 


>^>-H QJ 1 | 1 1 1 
33 33 Q DQcO-noncncQ. 


CX| 


H 
J 


-1 ' 

rJ 3 


H H h 

&H C4 H 



M 

O 



OH 



d 
cd 
o. 
o 

o. 
cu 

d 

0) 
N 

d 

0) 



4J CU 

Q) 43 

a rH rH 

H >. Cd 

Q 43 d 

I 4-1 Cd 

rH 0) Q. 

O 



I 

st 



O 

en 



sO 

oo 

? 

en 
cs 



en 

I 
o 



m 
i 



335 



C M O Tl 

cd o > -a 

T3 O CO Cd 

H >-, M 

X I 4-1 O" 

o oo c 



i-> M CO M 

C >, 0" O 

TJ 4J S CD 

l-l 0) IH 00 

oi a )-i 

X) O 01 " 

X) oi a co 



fi - H 

l-l CO CO 

J-i O -H 0) 

u-i co ui 

01 



U CO 

U M C lJ 

CO O >> Ol 

H U CO N 

O CO H 

CU M O O 

acU -H T-l 

H c: w 

0) OJ CO CO 

^ O to ca 

C3 O U M 

i-' co o a 

























01 OJ 


















i 






"^ "5 




Synonyms 




2 , 2-Dimethylpropionaldehyde 
a,a-Dimethylpropionaldehyde 
a , a -Dime thyl propanal 
Neopentanal 


_t-Bu tyl car boxalde hyde 
_t-Butylformaldehyde 


-Isopropyl-a-methylhydro- 
cinnamaldehyde 
Cyclamal 


Cyclamen aldehyde 
Aldehyde B 


j>-Isopropylphenyl-ct-methyl- 
propyl aldehyde 
ot-Methyl--isopropylhydro- 
ci nnamaldehyde 


2 -Me thyl-3-(j)-isopropylphenyl ) 
propionaldehyde 
3-(4-Isopropylphenyl)-2-nethyl 
propanal 


Isobutyr aide hyde 
Iso but anal 


Iso-butyraldehyde 
2-Methylpropionaldehyde 
Isopropyl aldehyde 
Isopropyl formaldehyde 
a-Methylpropionaldehyde 
Dimethyl acetaldehyde 


Methional 
3-( Me thyl thio) propionaldehyde 
B-(Methylthio) propionaldehyde 
3-Methylthiopropionaldehyde 
B-(Methylmercapto)propionaldeh> 
3-(Methylraercapto)propionaldehj 








1 




1 M 
M 

b c 












M 

cd 




T-l 


T3 


cd 




JC to 












co 

CX 




mpoun< 


C 

o 

CJ 

1 


a 
o 
u 
a 




01 O 

P a 

i oi 
1 CU 








c 

CO 

a 




o 
a 

/"x 

O 


0) 


o 
CJ 


_J 


4J 




sr N 

1 G 








o 




H 

x: 


d 


M-i 


2J 


0) TJ 

8 u 




M 0) 








a 

M 




H 


-M 


O 





3 




x: ^. 












x: 


a 


01 

H 


O 


1 




CU P*i 








J-l 




m 


O 

o 


1 




V > 


CM 




f 5 

01 








01 

f 
CN 




T 

CO 


CN 


^ 






















<! 

^*J 


XI 








7" 








CN 




CO 




4 








m 








1 




1 


W 


J 








ON 

1 








00 




0\ 


Pg 


w 








3 








30 

r-^ 




00 



336 







(U 










01" 3 , 






<H an 

co c 




T) 4J O 
H C O H 






U rH 




iH O -H CO (2 






T-f C 




O > H 4n ed 






i c 




M CO J3 4J 3 00 






ai eg 




<u e n c e n 










o -H oi 01 cd o 






CJ 




>, 00 rC 00 S 










rH 01 CO 






X n 




ijQ l-i . -.03 






0) C 

-H -H 




M fcO 4J rH 
(J l-l rH P! C Id 






CX >_i 




H QJ Cd -H Id JJ 






S J2 




4J 4J O C V-l 0) 






O 4-> 




01 CO -H M 01 6 






O 0) 




J2 0) 4J cd 60 










4J P-v D H *W 






4-1 >, 




d r-t 0) l-l O 






O CX 




>> O "4-1 






to co C 




CO CX Cd tO (U CO 
Q 0) t-l S 






H eg H 




U T3 M S M 






CO l-l 




O C Cd 3 (U O 






01 -C 
J3 U > 




4H ed f IH T3 4-i 

ex n -H 






4-1 3 cd 

C CO rH 

!> m 

CO CO 




01 0) 0) r-l rH 

4j C ex o ed 

Cd CO 0) H T3 

H ,c c J3 -^ en 






T3 > 




-O JJ -H CO U O 01 






O B )-i 




01 01 |2 CC] rH CO 






H D QJ 

cox; 




i VJ O W) rH r-l (U 
C 3 -H S*. O rC 






ed cx u 




4) >, JS JJ rC O 4-1 






00 6 td 




4J H W cd 4J p 
C O 01 0) 0) 4-1 >> 






O O rH 




M 0. 4J S CD 














Q> 










>*, 










0) 
iH 










i 

cd 








i 


C 








>, 


c 


01 01 


01 




O 


H 

1 


-d -a <u 


T3 









> > "O 


^l 




<Ti 


* eu 


Pyruvaldehyde 
Pyruvic aldehyde 
Ace tyl formaldehyde 
Acetylfonnyl 
a-Ketopropionaldeh 
2-Ketopropionaldeh 
Methylglyoxal 
Pyroracemic dldehy 


Malonaldehyde 
Malondialdehyde 
Malonyldialdehyde 
Malonic dialdehyde 
1 , 3-Propanedione 
1 ,3-Propanedialdeh 


0) 
T3 
>t 01 <H U 

O eU > 1 O 

J2 H 01 1 -i 
0) * 13 S 1 
(3 rH 'O rH 0) 12 (^ 
HedrHOCdl QJS-H 
OlCCCjiH CNCX*r-ICO 
HOlrHrHrHI OrHOO 

O CX>&-,>CXr-i ed 


4-Hydroxy-3,5-dirae 
cinnam aldehyde 
Sinapaldehyde 
Sinapic aldehyde 
Sinapyl aldehyde 


4-Hydroxy-3-raetho: 
Coniferaldehyde 
j>-Conifer aldehyde 
Ferulaldehyde 
Coniteryl aldehydi 










i 










& 










O -H 








i 


Cd 


















1 H 


0) CU 








in >, 


B a 








c 


1 O 








en cu 


en l-i 










I CX 


rH 






r>, CX rH 


>s 1 


C{J 








X CM 


C 


T 


i 


X C 


1 


cd 


^j 


J^ 


r-l O 0) 


U />, 


Ou 


^^ 


^3 




T3 rH 


O 

U 


Q 
U 


S 


>\ AJ o 

35 Q) M 


33 C? 


CX 

o 
c^ 


CU 
O 


o 

e 

i 


sir 
i 


1 01 

v' CX 
1 


1 





i 

CM 


m 


en 






30 


o 


4> 


3O 


i^ 


| 


l 


\ 


1 


1 
CO 


CM 


=0 


>o 


OO 

en 


f 


O 
1 


m 
l 


en 


1 


1 


fs^ 




20 


00 


CM 


o 


o 


m 


r>- 


m 


t-H 


CM 

^-4. 


* 



337 



a 
o 
a 





OJ 

o 

OJ 0) 42 
O T3 01 

42 42 rH 
OJ OJ CO 

H H O 
(0 (0 -H 

can 
c c c 

H -H i-l 

y u y 




o o o 


f*S ?! r*"l ^l 


42 43 42 


42 42 42 42 


4J 4J 4J 


4J 4J *J 4J 


0)0)0) 
f T? 

O|-M b| 


Iff* 
a a CM CM 



I >, 

(2 (2 C & N 

(2 C 13 CO C 

H -H -H cO CU 

L> O U CO CQ 



dehyde 



CU >i 
43 

, QJ Q) 
42 TJ T3 

>. Q) rH > 

43 T3 cfl 



0) 



OJ . - 

O cfl CM 

rH f2 I 

CO -H OJ 



QJ OJ 



42 43 
OJ Q} 
13 *O 



OJ 



H C 



(0 



O 

rH y 

O -H 

y ix, 

H I 



0) 

c o 

H ^ 
. rH rj 
H O -H 



rt 

-i ... 

>% O -H O 

(^ ^H t" -H 

CM Oi CM Cb 



O 
O 



(2 

8 
! 

O 



s 

1 

&t 



0) 

42 

a 



X co 

o a 

42 QJ 

4J a 

cu o 

*C n 

T a 



0} 

c! 

I OJ 

rH & 

fs o 

42 P 

u a. 
^ CM 

CM 



rH 

CO 

(2 
CU 

a 
o 

M 

ex 

CM 
I 



I 

CM 



(0 

tf 

0) 
CU 
O 

P 

a 
l 

CM 



H d 

>-. CJ 

U OJ 

I a 

m o 

M 

sf a 

l 

<r> CM 

N-/ I 
I 

cn 



(N 



3 5 
9 2g 



O 

m 



CO 



CO 

l 



co 
m 

30 
00 



m 
m 



o 
o\ 
I 

vO 



f 

o 

vO 

I 



338 







01 

-a cu 
>% c 

JZ H 
CU 



dehyde 



13 H 



cd 
X 
O 

-O .0 
H J-i 
M Cd 

cd >-, o 
c a. ^H 

H i-H >\ 

W >^ T3 
O 6 H 
O C VH 
H O > 

Tt^ 



c 


-(l-4)N,N'-bis- 
l)D-streptamini 














01 
T3 


t aldehyde 
c aldehyde 
ehyde 
al 


cu 
u 

Ol >% 


cu 
T? 


H 1 r-i 
?> r-1 >1 


?, 

J5 


0! -H T3 d 
CJ W rH cd 


TJ J3 

rS Q* 


^ 


Streptomycin A 
o-2-Deoxy-2-(meth 


1-glucopyranosj 
( ana no iminoraett 


Sesquisulf ate 
AgriStrep 
Streptobrettln 


Streptorex 
Vetstrep 


Tylosin A 
Tylosine 




rH 
C C 
O 03 O 
F-H rH rH 


n-Undecanal 


Hendecanal 
Hendecanaldehyde 


Undecyl aldehyde 
ri-Undecylic aide! 


Methyl _n-nonyl a 
Methyl nonyl ace 
Methylnonylaceta 
2-Methyl-l-undec 
Aldehyde M.N.A. 


Undecenoic aldeh 
9 -Undecylene aid 


Undecylenic aide 



z 

U 

s 

PH 



E- 
c/j 



C 
U 

! 

U 

a 
cu 



1 

< 
CJ 

w 



01 
f 

OJ 



NDECE 



O 
a\ 

vO 



1 

O 



CO 



en 



339 



340 

REFERENCES 

CHEMLINE Data Base. Bethesda, Md.: National Library of 

Medicine, April 1980. 

CHEMNAME. DIALOG Database. Palo Alto, Gal.: Lockheed 

Missiles & Space Co., Inc., June 1980. 

Fassett, D. W. Aldehydes and acetals, pp. 1959-1989. In 

Patty, F. A., Ed. Industrial Hygiene and Toxicology. 2nd 

rev. ed. D. W. Fassett and D. D. Irish, Eds. Vol. IT. 

Toxicology. New York: Interscience Publishers, 1963. 

Hawley, G. G. , Ed. The Condensed Chemical Dictionary. 9th 

ed. New York: Van Nostrand Reinhardt, 1977. 

Weast, R. C. , and M. J. Astle, Eds. Handbook of Chemistry 

and Physics. 59th Edition. 1978-1979. Cleveland, Ohio: 

The Chemical Rubber Co., 1978. 

Windholz, M. , S. Budavari, L. Y. Stroumtsos, and 

M. N. Fertig, Eds. The Merck Index. An Encyclopedia of 

Chemicals and Drugs. 9th ed. Rahway, N. J. : Merck & Co., 

Inc., 1976.